β-Lactam antibacterial agents

ABSTRACT

Compounds are described of the formula (II): ##STR1## wherein R 1  is a group such that CO 2  R 1  is an ester group; A 1  is a hydrogen atom; and A 2  is a group CR 2  R 3  R 4  wherein R 2  is a hydrogen atom or a hydroxyl group; R 3  is a hydrogen atom or a lower alkyl group; and R 4  is a hydrogen atom or a lower alkyl group, a benzyl group, a phenyl group or is joined to R 3  to form part of a C 5-7  carboxylic ring or is a group of the formula CH(OH)R 5  or CHX wherein R 5  is a hydrogen atom or lower alkyl group and X is an oxygen atom or a CR 6  R 7  group where R 6  is a hydrogen atom or a lower alkyl, phenyl, CN, CO 2  R 8  where R 8  is a lower alkyl, phenyl or benzyl group and R 7  is a hydrogen atom or a lower alkyl group or is joined to R 6  to form part of a C 5-7  carbocyclic ring. These compounds have been found to possess antibacterial properties. The preparation of these compounds is described.

CROSS REFERENCE

This is a continuation of Ser. No. 887,844, filed Mar. 17, 1978, now abandoned.

The present invention relates to β-lactam antibacterials, to compositions containing them, to the process for their preparation and to compounds useful as intermediates in that process.

British Pat. No. 1,467,413 discloses that the compound of the formula (I): ##STR2## and its salts may be obtained via the fermentation of strains of Streptomyces olivaceus. We have now found that a distinct class of synthetic antibacterial agents may be prepared.

Accordingly the present invention provides the compounds of the formula (II): ##STR3## wherein R₁ is a group such that CO₂ R₁ is an ester group; A₁ is a hydrogen atom or a methyl group; and A₂ is a hydrogen atom or a group CR₂ R₃ R₄ wherein R₂ is a hydrogen atom or a hydroxyl group; R₃ is a hydrogen atom or a lower alkyl group; and R₄ is a hydrogen atom or a lower alkyl group, a benzyl group, a phenyl group or is joined to R₃ to form part of a C₅₋₇ carbocyclic ring or is a group of the formula CH(OH)R₅ or CHX wherein R₅ is a hydrogen atom or lower alkyl group and X is an oxygen atom or a CR₆ R₇ group where R₆ is a hydrogen atom or a lower alkyl, phenyl, CN, CO₂ R₈ or CO.R₈ where R₈ is a lower alkyl, phenyl or benzyl group and R₇ is a hydrogen atom or a lower alkyl group or is joined to R₆ to form part of a C₅₋₇ carbocyclic ring.

When used herein the term "lower" means the group contains up to 8 carbon atoms. When used herein the term "lower alkyl" more suitably means a group of up to 6 carbon atoms which is most suitably a straight chain group of up to 4 carbon atoms.

One suitable sub-group of compounds of the formula (II) is that of the formula (III): ##STR4## wherein R₁ and A₁ are as defined in relation to formula (II):

Suitably A₁ is a methyl group. Suitably A₁ is a hydrogen atom.

A further suitable sub-group of compounds of the formula (II) is that of the formula (IV): ##STR5## wherein R₁, R₂, R₃ and R₄ are as defined in relation to formula (II).

Suitably R₂ is a hydrogen atom. Suitably R₂ is a hydroxyl group. Suitable values for R₄ include the hydrogen atom and the methyl, ethyl, n-propyl, phenyl, CHO, CH═CHCO₂ R₉, CH═CHCOR₉ and CH═CHR₁₀ groups wherein R₉ is a methyl, ethyl or benzyl group and R₁₀ is a hydrogen atom or a methyl, ethyl or benzyl group.

Suitable values for R₃ include the hydrogen atom and the methyl, ethyl and n-propyl groups.

Favourably R₃ is a hydrogen atom or a methyl group.

Favourably R₄ is a hydrogen atom or a methyl group.

A suitable sub-group of compounds of the formulae (IV) is that of the formula (V): ##STR6## wherein R₁ and X are as defined in relation to formula (II).

Suitably X is an oxygen atom. Suitably X is a CR₆ R₇ group where R₆ and R₇ are defined as in relation to formula (II).

Favourably CR₆ R₇ is a CHCOR₉ or CHCO₂ R₉ group where R₉ is as defined in relation to formula (IV). Favourably CR₆ R₇ is a CHCN group.

A further apt sub-group of compounds of the formula (IV) is that of the formula (VI): ##STR7## wherein R₁ is as defined in relation to formula (IV), R₁₁ is a hydrogen atom or a lower alkyl group and R₁₂ is a hydrogen atom or a lower alkyl group.

Suitably R₁₁ is a hydrogen atom or a methyl group. Suitably R₁₂ is a hydrogen atom or a methyl group.

Yet another apt sub-group of compounds of the formula (III) is that of the formula (VII): ##STR8## wherein R₁ is as defined in relation to formula (II) and R₁₃ is a hydrogen atom or a methyl, ethyl or hydroxymethyl group.

The compounds of the formula (IV)-(VII) may have the cis-configuration about the β-lactam ring. The compounds of the formulae (IV)-(VII) may alternatively have the trans-configuration about the β-lactam ring. If desired these compounds may be presented as mixtures of cis- and trans-compounds although it is not normally preferred to so do.

The compounds of the formula (II)-(VII) are generally provided as mixtures of 5R and 5S forms but separated forms are also within the ambit of this invention.

Suitable values for R₁ in the compounds of the formula (II)-(VII) include alkyl groups of up to 12 carbon atoms, alkenyl groups of up to 8 carbon atoms, alkynyl groups of up to 8 carbon atoms or a phenyl or benzyl group or one of the aforementioned groups substituted by a lower alkoxyl, lower acyloxyl, halogen or nitro group.

Aptly R₁ is a lower alkyl group optionally substituted by a lower alkoxyl group.

Aptly R₁ is a benzyl group optionally substituted by a lower alkoxyl or nitro group or chlorine atom.

Favoured values for R₁ include the groups of the sub-formulae (a) or (b): ##STR9## wherein A₃ is a hydrogen atom or a methyl group; A₄ is a lower alkyl, lower alkoxyl, phenyl, phenoxyl, benzyl or benzyloxyl group; A₅ is a hydrogen atom or a methyl or methoxyl group and A₆ is a hydrogen atom and methyl or methoxyl group.

Certain preferred groups R₁ include the methyl, methoxymethyl, benzyl, p-methoxybenzyl, acetoxymethyl, pivaloyloxymethyl, α-ethoxycarbonyloxyethyl, phthalidyl, phenacyl and phthalimidomethyl groups.

A favoured group R₁ is the phthalidyl group.

A further favoured group R₁ is the benzyl group.

Another favoured group R₁ is the p-nitrobenzyl group.

This invention also provides an antibacterial pharmaceutical composition which comprises a compound of the formula (II) and a pharmaceutically acceptable carrier.

Most suitably the composition will be in unit dosage form and will comprise 25-1000 mg and more usually 50-500 mg of a compound of the formula (II).

Preferably the compound of the formula (II) present in such compositions will be in-vivo hydrolysable to the parent acid or its salt.

The compositions of this invention may beneficially also comprise a penicillin or cephalosporin. Certain particularly suitable penicillins for use in these compositions include amoxycillin trihydrate and sodium amoxycillin.

The compositions of this invention may be used for the treatment of bacterial infections due to suceptible bacteria such as gram positive bacteria such as Staphylococcus aureus.

The compositions may be administered in conventional manner, for example parenterally or by intramammary administration for the treatment of mastitis in cattle.

The present invention also provides a process for the preparation of a compound of the formula (II) which process comprises the ring closing elimination of the elements of O═PA₇ A₈ A₉ from a compound of the formula (VIII): ##STR10## wherein R₁, A₁ and A₂ are as defined in relation to formula (II) and A₇, A₈ and A₉ are lower alkyl, phenyl or methoxyphenyl groups.

Aptly A₇, A₈ and A₉ are all phenyl groups. Other apt values for each of A₇, A₈ and A₉ is the p-methoxyphenyl group.

Suitably A₂ is a hydrogen atom.

Suitably A₂ is a group CR₂ R₃ R₄ as defined in relation to formula (IV).

The elimination reaction tends to occur spontaneously at relatively low temperatures, for example -20° C. to 0° C. when A₁ is a hydrogen atom or at a higher temperature, for example at about 100° C. when A₁ is methyl.

The solvent used for the proceeding process will be an inert organic solvent such as ethyl acetate, benzene or toluene.

The compounds of the formula (VIII) wherein A₁ is hydrogen may be prepared by a reaction sequence such as: ##STR11##

This invention provides a process for the preparation of a compound of the formula (VIII) as hereinbefore defined which process comprises the ozonolysis in the presence of excess trifluoroacetic acid of a compound of the formula (IX): ##STR12## wherein R₁, A₁, A₂, A₇, A₈ and A₉ are as defined in relation to formula (VIII) and thereafter neutralising the trifluoroacetic acid.

This ozonolysis is normally carried out in an inert solvent such as ethyl acetate, or methylene chloride.

The process is normally carried out at a depressed temperature, for example -80° to -20° C., more usually at about -70° to -50° C. In general ozone is passed through the solution until a light blue colour is produced. At this point excess ozone may be removed by passing through an inert gas. The intermediate ozonide may now be reduced by the addition of a conventional reducing agent such as triphenylphosphine. The trifluoroacetic acid should now be neutralised for example by the addition of a solution of a base such as sodium bicarbonate solution at about 0° C.

Once the neutralisation is complete the reaction is usually allowed to warm to ambient temperature under which conditions the compound spontaneously cyclises.

This invention also provides a process for the preparation of a compound of the formula (IX) as hereinbefore defined where A₂ is a CR₂ R₃ R₄ group which process comprises reacting a compound of the formula (X): ##STR13## wherein A₇, A₈, A₉ and R₁ are as defined in relation to formula (VIII) with a base to generate an anion of the formula (XI): ##STR14## wherein A₇, A₈, A₉ and R₁ are as defined in relation to formula (VIII); which is then reacted with a compound of the formula (XII), (XIII) or (XIV): ##STR15## wherein R₃, R₄ and R₅ are as defined in relation to formula (II) and Y is a moiety readily displaced by a nucleophile.

Suitable values for Y include Cl, Br, I. OSO₂ CH₃ O.SO₂.C₆ H₄ CH₃ or the like. Particularly suitable values for Y include Cl, Br and I.

The generation and reaction of the anion of the formula (XI) is brought about in an inert organic medium under aprotic conditions. Suitable solvents for the reaction include hydrocarbons such as hexane, tetrahydrofuran, dimethoxyethane, formdimethylamide, hexamethylphosphorus triamide or mixtures thereof.

Since the anion is a highly reactive species its generation and reaction are normally affected at a depressed temperature, for example at or below 0° C., more suitably -80° to -60° C.

The base used to generate the anion of the formula (XI) will be a strong base of low nucleophilicity. Suitable bases include lithium alkyls such as lithium butyl, lithium amides such as lithium di-isopropylamine or lithium hexamethyldisilylamide or the like.

Once formed the anion may be quenched by the addition of the dry compound of the formula (XII), (XIII) or (XIV). The compound of the formula (XII), (XIII) or (XIV) may be added neat or dissolved in a dry inert solvent.

It is most suitable to carry out the preceding reactions under an inert atmosphere, for example under dry nitrogen or dry argon.

The preceding reaction normally produces a mixture of the cis- and trans-compounds of the formula (XV) and (XVI): ##STR16## in admixture with their C₅ enantiomers.

These cis- and trans-substituted compounds can generally be separated from each other by chromatography, for example over silica gel gradiently eluting with solvent mixtures such as ethyl acetate/hexane.

The compounds of the formula (X) as hereinbefore defined may be prepared by the reaction of a compound of the formula (XVII): ##STR17## wherein R₁ is as defined in relation to formula (II) with a phosphine of the formula PA₇ A₈ A₉ wherein A₇, A₈ and A₉ are as defined in relation to formula (X).

This reaction is normally carried out in an inert solvent such as dioxane, tetrahydrofuran or the like in the presence of at least 1 equivalent of a base such as 2,6-lutidine or like base of relatively low nucleophilicity. In general the reaction is carried out at a non-extreme temperature such as about 5°-35° C.

The compound of formula (XVII) may be prepared by the reaction of thionyl chloride on a corresponding compound of the formula (XVIII): ##STR18## wherein R₁ is as defined in relation to formula (II).

This reaction takes place under similar conditions to the preparation of the compound of the formula (X) except that a depressed temperature, for example -30° to -10° C., is used.

The compound of the formula (XVIII) may be prepared by the reaction of a compound of the formula (XIX): ##STR19## and a compound of the formula (XX): ##STR20## wherein R₁ is defined as in relation to formula (II).

This preceding reaction is conveniently carried out by reacting the compounds together in refluxing benzene in such a manner that any water present is continuously removed.

The compounds of the formula (II) wherein CR₂ R₃ R₄ is a CH₂.CH═X group wherein X is as defined in relation to formula (II) may also be prepared by the following reaction sequence: ##STR21##

The compounds of the formula (XXI) may be obtained by the method of Paquett et al, J. Amer. Chem. Soc., 90, 2897, (1968).

The compounds of the formula (XXI) prepared in this manner have the cis-configuration at the ring junction and this configuration is preserved in the compounds of the formulae (XXII)-(XXVII).

The compounds of the formula (XXII) may be prepared by the reaction of a compound of the formula (XXI) with a compound of the formula (XX) as hereinbefore defined under conditions similar to those described for the reaction of a compound of the formula (XIX) and (XX).

Reaction of a compound of the formula (XXII) with thionyl chloride under conditions similar to those described for the reaction of thionyl chloride with a compound of the formula (XVIII) may be used to prepare the compounds of the formula (XXIII).

The compounds of the formula (XXIII) may be converted into the compounds of the formula (XXIV) by reaction with a phosphine of the formula PA₇ A₈ A₉ under conditions similar to those used for the preparation of a compound of the formula (X).

The present invention also provides a process for the preparation of the compounds of the formula (XXV): ##STR22## wherein A₇, A₈, A₉ and R₁ are as defined in relation to formula (X) which process comprises the ozonolysis of a compound of the formula (XXIV): ##STR23## wherein R₁, A₇, A₈ and A₉ are as defined in relation to formula (IX).

The ozonolysis reaction may be brought about under conditions similar to those described for the ozonolysis of the compounds of the formula (IX).

Once formed the compounds of the formula (XXV) undergo spontaneous cyclisation with elimination of the elements of a compound of the formula O═PA₇ A₈ A₉ and the formation of a compound of the formula (XXVI). This cyclisation reaction also forms part of this invention.

The compounds of the formula (XXVI) tend to be somewhat unstable so that it is often more suitable to react them in situ with an agent such as a compound of the formula (XXVIII): ##STR24## or chemically equivalent agents wherein R₆ and R₇ are as defined in relation to formula (II).

This reaction of the compounds of the formula (XXVI) and (XXVIII) occurs under conventional reaction conditions for reaction of an aldehyde and a phosphorane and gives the olefins of formula (XXVII).

The compounds of the formula (XVIII) and (XXII) may also be prepared by the reaction of a compound of the formula (XIX) or (XXI) with glyoxylic acid and thereafter esterifying the resulting compound of the formula (XXIXa) or (XXIXb) ##STR25## in a conventional manner.

Certain trans substituted compounds may be prepared by the following reaction scheme in which an allyl halide such as allyl bromide is reacted with the anion (XI) in similar manner to the alkylations previously described. The ozonolysis of the resulting compound may be carried out as described for ozonolysis of a compound of the formula (XXIV) and the ring closure of the compound of the formula (XXXI) may be carried out as described for the compound of the formula (XXV). ##STR26##

The compounds of the formula (VIII) wherein A₁ is a methyl group may be prepared by a reaction sequence such as ##STR27## H-(Propan-2-one)azetidin-2-one may be prepared as described in Example 22 herein. Reaction of this compound with a glyoxylic acid ester to yield a compound of the formula (XXXIII) may be carried out under conditions similar to those described for an analogous reaction of a corresponding vinyl compound. (Alternatively the 4-(Propan-2-one)azetidin-2-one may be reacted with glyoxylic acid and the resulting compound esterified thereafter). The reaction of the resulting hydroxy compound with thionyl chloride and the reaction of the resulting chloro compound with a phosphene may be brought about in a manner similar to that described hereinbefore for the preparation of a compound of the formula (X).

The following Examples illustrate the invention:

EXAMPLE 1 Benzyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate ##STR28## (i) 7-(1-Hydroxy-1-benzyloxycarbonylmethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR29##

Benzyl glyoxylate (2.73 g) was refluxed in benzene (25 ml) with provision for the removal of water. After 45 minutes 8-oxo-7-azabicyclo[4,2,0]oct-3-ene (1) (ref: I. A. Paquette and T. Kakihana, J. Amer. Chem. Soc., 1968, 90, 2897) (1.23 g) was added and refluxing continued for 3 hours. Removal of solvent under reduced pressure followed by chromatography gave two separate isomers of the alcohol (2)(90%) Isomer I, m.p. 92°-93°, λ_(max) (CHCl₃) 3450, 1750 (b) cm⁻¹. δppm (CDCl₃) 1.76-2.73 (4H, m, 2-CH₂), 3.12-3.33 (1H, m, β-lactam proton), 3.76-3.93 (1H, m, β-lactam proton), 4.40 (1H, d, J 6 Hz, exch., D₂ O), 5.16 (2H, s, CH₂), 5.47 (1H, d, J 6 Hz collapsing to s on D₂ O exch., CH-OH), 5.67-5.83 (2H, m, CH═CH), 7.34 (5H, Ar). M⁺ at m/e 287 (Found: C, 66.2; H, 5.9; N, 4.9. C₁₆ H₁₇ NO₄ requires C, 66.9; H, 6.0; N, 4.9%). Isomer II, m.p. 100°-101°, ν_(max) (CHCl₃) 3450, 1750 (b), δppm (CDCl₃) 1.80-2.63 (4H, m,2-CH₂), 3.13-3.36 (1H, m, β-lactam proton), 3.93-4.13 (1H, m, β-lactam proton), 4.20 (1H, bs, exch., D₂ O), 5.16 (2H, s, CH₂), 5.50 (1H, b, sharpening to s on D₂ O exchange), 5.50-6.00 (2H, m, CH═CH), 7.34 (5H, Ar). H⁺ at m/e (Found: C, 67.2; H, 6.0; N, 4.8. C₁₆ H₁₇ NO₄ requires C, 66.9; H, 6.0; N, 4.9%).

(ii) 7-(1-Benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR30##

The alcohol (2, as mixture of isomers, 2.2 g) in THF (50 ml) was cooled to -20°. Lutidine (1.5 g) was added followed by thionyl chloride (1.0 ml). After stirring at -20° for 20 min, the solution was filtered and evaporated to dryness; final removal of the last traces of excess thionyl chloride was by evaporation twice from toluene. The residue in dioxan (20 ml) was treated with triphenylphosphine (4.02 g) and lutidine (1.64 g) and left stirring overnight at room temperature. The lutidine hydrochloride was separated by filtration, and the filtrate evaporated to dryness and chromatographed to give (3, 1.5 g) as an amorphous solid, ν_(max) (CHCl₃) 1730, 1620 cm⁻¹.

(iii) Benzyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR31##

The phosphorane (3, 0.2 g) in ethyl acetate (10 ml) was treated with trifluoroacetic acid (0.25 ml). The solution was cooled (-65°) and treated with ozone until the reaction solution showed a slight blue colouration. Argon was blown through the solution to remove excess ozone, and then triphenylphosphine (0.1 g) was added. After five minutes the reaction was transferred to an ice-bath and stirred vigorously with aqueous (5%) sodium bicarbonate solution (10 ml) for 45 minutes. The organic phase was separated, dried, evaporated and chromatographed to give the product (4, 42 mg as a gum), ν_(max) (CHCl₃) 1780, 1725, 1610 cm⁻¹. δppm (CDCl₃) 2.50-3.00 (4H, m, 2×CH₂), 3.87-4.11 (1H, m, C6-H), 4.46 (1H, dt, J 6 Hz, 9 Hz C5-H; collapses to d, J 6 Hz on irradiation at δ2.60); 5.21 (2H, s, benzyl CH₂), 6.45 (1H, t, J 2 Hz, C3-H), 7.30 (5H, s, Ar), 9.70 (1H, s, CHO). M⁺ at m/e 285. The β-lactamase inhibition I₅₀ values in μg/ml for (4) were as follows:

    ______________________________________                                         Enterobacter P99   1.6                                                         Pseudomonas aeruginosa A                                                                          >>40                                                        Proteus mirabilis C889                                                                            2.1                                                         Klebsiella aerogenes E70                                                                          >>40                                                        Escherichia coli JT4                                                                              <1.2                                                        Pseudomonas dalgleish                                                                             1.0                                                         Staphylococcus aureus Russell                                                                     >10                                                         ______________________________________                                    

EXAMPLE 2 Benzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR32##

The phosphorane (3, 0.2 g) in ethyl acetate (10 ml) was treated with trifluoroacetic acid (0.25 ml) and subjected to ozonolysis and work up as in Example 1 (iii) the crude product containing (4) was dissolved in chloroform (5 ml) and treated with methoxycarbonylmethylene triphenylphosphorane (0.124 g) and left for 1 hour at room temperature. The solution was evaporated to dryness and chromatographed to give the product (5) (45 mg), m.p. 81°-82° (from ether), ν_(max) (CHCl₃) 1780, 1720, 1650, 1610 cm⁻¹. δppm (CDCl₃) 2.68 (2H, dd, J 9 Hz, 3 Hz, C4-CH₂ ; collapsing to d J 3 Hz on irradiation at δ4.3); 2.40-2.90 (2H, m, C6 side-chain CH₂), 3.67 (3H, s, OMe), 3.67-3.74 (1H, m, C6-H), 4.35 (1H, dt, J 6 Hz, 9 Hz, C5-H, collapsing to d J 6 Hz on irradiation at δ2.6); 5.20 (2H, s, benzyl CH₂), 5.80 (1H, d, J 15 Hz, trans MeO₂ CCH═CH--), 6.45 (1H, t, J 3 Hz, C3-H, collapsing to s on irradiation at δ2.6), 6.84 (1H, dt, J 15 Hz, 6 Hz, trans --CH═CH-CH₂), 7.32 (5H, s, Ar). (Found: M, 341.1270. C₁₉ H₁₉ NO₅ requires M, 341.1263).

The minimum concentrations of this compound required to inhibit the growth of the following bacteria are given below:

    ______________________________________                                         Organism          MIC (μg/ml) agar                                          ______________________________________                                         Bacillus subtilis A                                                                              20                                                           Citrobacter freundii E8                                                                          20                                                           Klebsiella aerogenes A                                                                           20                                                           Shigella sonnei MB 11967                                                                         20                                                           Staph. aureus Russell                                                                            2                                                            Staph. aureus 1517                                                                               2                                                            ______________________________________                                    

A small amount (6 mg) of the cis-isomer (about the C-6 side-chain double bond) of (5) was also obtained.

EXAMPLE 3 2,2,2-Trichloroethyl-6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR33## (i) 7-(1-Hydroxy-1-2,2,2-trichloroethoxycarbonylmethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR34##

2,2,2-Trichloroethylglyoxylate (0.78 g) was refluxed in benzene (15 ml) with provision for the removal of water (0.5 hrs). The azetidinone (1) (0.287 g) was added and refluxing continued for 1 hour. Removal of the solvent and chromatography gave the alcohol (6) (80%). Isomer I m.p. 85°-88°, ν_(max) (CHCl₃) 3500, 1770 (ester), 1750 (β-lactam) cm⁻¹. δppm (CDCl₃) 2.00-2.80 (4H, m, 2×CH₃), 3.30-3.40 (1H, m, β-lactam proton), ca 3.70 (1H, bs, exch, D₂ O, OH), 4.10-4.25 (1H, m, β-lactam proton), 4.80 (2H, s, CH₂), 5.50 (1H, s, CH), 5.72-5.91 (2H, m, CH═CH). (Found: C, 40.3; H, 3.7; N, 4.2. C₁₁ H₁₂ Cl₃ NO₄ requires C, 40.2; H, 3.7; N, 4.3%). Isomer II m.p. 119°-121°, had similar spectroscopic properties.

(ii) 7-(1-Trichloroethoxycarbonyl-1-triphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR35##

The alcohol (6) (6.0 g as a mixture of isomers) in THF (75 ml) was converted to the chloride as in example 1 (ii) using thionyl chloride (2.61 ml) and lutidine (4.25 ml). The crude chloride in dioxan (75 ml) was reacted with triphenylphosphine (9.6 g) and lutidine (4.25 ml) as for the benzyl ester to give the phosphorane (7), (6.0 g) as a foam, ν_(max) (CHCl₃) 1740, 1630 cm⁻¹.

(iii) 2,2,2-Trichloroethyl-6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR36##

The phosphorane (7) (0.2 g) was dissolved in EtAc (10 ml) and trifluoroacetic acid (1 ml) and subjected to ozonolysis and work up as for the benzyl ester in example 1 (iii) The crude reaction product in chloroform (3 ml) was treated with carbomethoxymethylene triphenylphosphorane (117 mg) and left at R.T. for 0.5 hours. Evaporation and chromatography gave (8) (40 mg) m.p. 101°-102°, ν_(max) (CHCl₃) 1785, 1735, 1720, 1660, 1615 cm⁻¹. δppm (CDCl₃) 2.74 (2H, dd, J 10 Hz, 3 Hz, C4-CH₂), 2.30-2.90 (2H, m, CH₂), 3.65 (3H, s, OMe), 3.60-3.90 (1H, m, C6-H), 3.38 (1H, dt, J 6 Hz, 10 Hz, C5-H), 4.70 and 4.86 (2H, ABq, J 12 Hz, CH₂ CCl₃), 5.80 (1H, d, J 15 Hz plus further slight coupling trans MeO₂ C-CH═CH--CH₂), 6.60 (1H, t, J 3 Hz, C3-H), 6.84 (1H, dt, J 15 Ez, 6 Hz, trans CH═CH--CH₂). λ_(max) (EtOH) 209 nm (ε12,100), 273 nm (ε3110).

The concentrations of this compound required to inhibit the growth of the following bacteria are given below.

    ______________________________________                                         Organism           μg/ml (agar)                                             ______________________________________                                         B. Subtilis A      20                                                          Citrobacter freundii E8                                                                           20                                                          Klebsiella aerogenes A                                                                            20                                                          Shigella sonnei MB 11967                                                                          20                                                          Staph. aureus Oxford                                                                              ≦2                                                   Staph. aureus Russell                                                                             ≦2                                                   Staph. aureus 1517 ≦2                                                   Strep faecalis I   20                                                          Strep pneumoniae   20                                                          Strep pyogenes CN10                                                                               20                                                          ______________________________________                                    

A small amount (6 mg, m.p. 70°-72°) of the cis-isomer (about the C-6 double bond) was also obtained.

EXAMPLE 4 Benzyl 6-(2-hydroxy-2-propyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR37## (i) 4-Allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(2-hydroxy-2-propyl)azetidin-2-one ##STR38##

A solution of N-isopropylcyclohexylamine (0.60 g) in dry tetrahydrofuran (10 ml) was stirred under argon and cooled to -78° C. This was treated with a 2.5 M solution of n-butyl lithium in n-hexane (1.70 ml). After ten minutes, a solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl))azetidin-2-one (9) (1.00 g) in dry tetrahydrofuran (10 ml) was added. Five minutes was allowed for the formation of the C(3) carbanion which was then quenched by the addition of dry acetone (0.71 ml). The cooling bath was then removed and the mixture stirred for a further ten minutes before it was neutralised with acetic acid (0.56 g). The solvent was evaporated under reduced pressure and the residue chromatographed on silica gel 60 (<230 mesh), eluting with ethyl acetate/60°-80° petroleum ether mixtures grading from 1:1 to 7:3. This gave a mixture of the cis and trans-isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(2 -hydroxy-2-propyl)azetidin-2-one (0.76 g; 71%) (10) and (11), ν_(max) (CHCl₃) 3000, 1735 and 1620 cm⁻¹.

It was possible to obtain a substantial separation of the cis- and trans-isomers by further chromatography on silica gel 60 (<230 mesh), eluting with ethyl acetate/60°-80° petroleum ether mixture grading from 1:1 to 7:3.

(ii) Benzyl 6-(2-hydroxy-2-propyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR39##

The cis-isomer of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(2-hydroxy-2-propyl)azetidin-2-one (10) (0.188 g) was dissolved in ethyl acetate (14 ml). An excess of trifluoroacetic acid (0.37 g) was added and the mixture cooled to -78° C. Ozone was passed into the reaction mixture until it was pale blue in colour. Argon was then bubbled through the solution until all the excess ozone had been removed. A solution of triphenylphosphine (0.085 g) in ethyl acetate was added and argon bubbled through the mixture for a further ten minutes. The reaction flask was then transferred to an ice bath and a saturated aqueous solution of sodium bicarbonate (20 ml) was added and the mixture stirred vigourously under argon for thirty minutes. The ethyl acetate layer was separated, washed with brine and dried.

The solution containing (12) was left at room temperature for thirty-six hours. During this time, the cyclisation reaction was followed by thin-layer chromatography and it was seen that a slow moving spot gradually decreased in intensity along with an increase in the intensity of a faster moving spot which corresponded to the required cis-product. The ethyl acetate was evaporated off under reduced pressure and the residue was purified by chromatography on silica gel 60 (<230 mesh), eluting with ethyl acetate/60°-80° petroleum ether 1:1. The product was a crystalline material (0.048 g; 49%), which could be recrystallised from ethyl acetate/60°-80° petroleum ether; m.p. 122°-124°. ν_(max) (CHCl₃) 2950, 1770 and 1720 cm⁻¹ ; λ_(max) (EtOH) 273 nm (ε 4800). δ ppm (CDCl₃) 7.36 (5H, br. s, phenyl) 6.59 (1H, t, J 21/2 Hz, C3-H), 5.28 and 5.30 (2H, inside signals of ABq, --CH₂ --Ph), 4.35 (1H, dt, J 61/2 and 9 Hz, C5-H), 3.83 (1H, ddd, J 18, 9 and 21/2 Hz, C4-H), 3.59 (1H, d J 61/2 Hz, C6-H), 2.68 (1H, ddd, J 18, 9 and 21/2 Hz, C4-H), 1.74 (1H, br. s, --OH), 1.30 and 1.54 (6H, two singlets, C-CH₃ 's). λ_(max) (ethanol). (M⁺ at m/e 301.1315 C₁₇ H₁₉ NO₄ requires 301.1314. Found: C, 67.7; H, 6.5; N, 4.5%. C₁₇ H₁₉ NO₄ requires C, 67.8; H, 6.4; N, 4.7%).

The concentrations of this compound required to inhibit the growth of the following bacteria are given below.

    ______________________________________                                         Organism           μg/ml (agar)                                             ______________________________________                                         Enterobacter cloaceae N1                                                                          20                                                          Klebsiella aerogenes A                                                                            ≦2                                                   Serratia marcescens US20                                                                          20                                                          Shigella sonnei MB 11967                                                                          ≦2                                                   Staph. aureus Oxford                                                                              ≦2                                                   Staph. aureus Russell                                                                             ≦2                                                   ______________________________________                                          ##STR40##

The trans-isomer of 4-alkyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(2-hydroxy-2-propyl)azetidin-2-one (11) (0.365) was treated as in (a) above. In this case, however, the formation of the bicyclic system was complete after stirring the basified reaction mixture from the ozonolysis for thirty minutes. The required product (0.048 g; 25%) was obtained after chromatography; ν_(max) (CHCl₃) 2950, 1780 and 1720 cm⁻¹ ; δ ppm (CDCl₃) 7.28 (5H, br, phenyl), 6.36 (1H, t, J 2 Hz, C3-H), 5.20 (2H, s, --CH₂ Ph), 4.20 (1H, dt J 3 and 8 Hz, C5-H), 3.16 (1H, d J 3 Hz, C6-trans H), 2.95 and 2.65 (2H, two ddd's J 18, 8 and 2 Hz, C4-H's), 1.78 (1H, br. s, --OH), 1.30 and 1.37 (6H, two singlets, C--CH₃ 's); (M⁺ at m/e 301.1303. C₁₇ H₁₉ NO₄ requires 301.1314).

(c) The procedure described in section ii (a) was carried out on the mixture of the cis- and trans-isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(2-hydroxy-2-propyl)azetidin-2-one (0.76 g) as obtained in Example(a). After work-up and chromatographic separation, pure cis (0.045 g; 11%) and trans (0.100 g; 25%) isomers of benzyl 6-(2-hydroxy-2-propyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate were obtained.

(iii) Preparation of 4-allyl azetidin-2-one ##STR41##

1,4 Pentadiene (16) (30 g) and chlorosulphonyl isocyanate (17) (35.4 ml) were mixed and allowed to stand at room temperature for 3 days, in a pressure bottle. The thick, dark syrup, obtained was diluted with methylene chloride (500 ml) and added dropwise to a stirred solution of sodium sulphite (66 g) in water (240 ml). The pH was maintained between 6.5 and 7.5 by the addition of 10% aqueous potassium hydroxide (600 ml in total). The lower organic phase was separated and the aqueous phase extracted (x 2) with ethyl acetate. The combined organic extracts were dried over magnesium sulphate, filtered, and evaporated to give the crude azetidinone (18) as a red oil (16.05 g). This was sufficiently pure for use in subsequent reactions e.g. Example 4(iv), but could be further purified by distillation b.p. 76°-80°/0.2 mm. ν_(max) (CHCl₃) 3490, 1770 (strong), 1650 (weak) cm⁻¹. δ ppm (CDCl₃) 2.39 (2H, t, J 6 Hz, CH₂), 2.61 (1H, ddd, J 14 Hz, 2 Hz, 1.5 Hz, collapsing with D₂ O to dd, J 14 Hz, 2 Hz, C3-H), 3.10 (1H, ddd, J 14 Hz, 5 Hz, 2 Hz, collapsing with D₂ O to dd, J 14 Hz, 5 Hz, C3-H), 3.55-3.91 (1H, m C4-H), 4.98-6.21 (3H, complex pattern, CH═CH₂), 6.67 (1H, broad s, exch. D₂ O) (Found: M, 111.0683. C₆ H₉ NO requires M, 111.0684).

(iv) Preparation of 4-allyl-1-(1-hydroxy-1-benzyloxycarbonylmethyl) azetidin-2-one ##STR42##

Benzyl glyoxylate hydrate (6 g) in benzene (120 ml) was refluxed for 0.5 hours in a Dean-Stark apparatus to remove the water. The azetidinone (18) (2.13 g) was added and the reaction mixture refluxed for 4 hours. The solution was cooled, evaporated, and chromatographed on silica gel, eluting with ethyl acetate-petroleum ether mixtures to give a colourless oil (5.6 g) consisting mainly of the isomers of (19) and sufficiently pure for use in subsequent reactions. Rechromatography of a small portion of this oil, eluting with chloroform gave (19) as an oil. ν_(max) (CHCl₃) 3420, 1750 (strong), 1640 (weak) cm⁻¹. δ ppm (CDCl₃) 1.90-3.05 [4H, m, including δ 2.53 (1H, dd, J 15 Hz, 2 Hz, C3-H), 2.92 (1H, dd, J 15 Hz, 5 Hz, C3-H), obscurring 2H, CH₂ ], 4.52 (1H, broad, s, exch. D₂ O, --OH), 4.85-5.90 [6H, m, including δ 5.40 (1H, broad, collapsing with D₂ O to singlet, H--C--OH)+complex pattern for CH₂ Ph and CH═CH₂ ], 7.29 (5H, s).

(v) Preparation of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidin-2-one ##STR43##

A stirred solution of the alcohol (19) (6.6 g) in dry tetrahydrofuran (200 ml), under argon, was cooled to -20°, and treated with lutidine (5.13 g) in tetrahydrofuran (10 ml). Thionyl chloride (5.70 g) in tetrahydrofuran (20 ml) was added dropwise. After allowing to reach 0° over 20 minutes, the precipitated solid was filtered off, washing with dry toluene.

The combined filtrate and washings were evaporated to dryness and the residue taken up in dry toluene, filtered and evaporated. The gum obtained was taken up in dioxan (200 ml) and treated with triphenylphosphine (12.6 g) and lutidinc (5.53 ml). After stirring under argon at room temperature for 3 hours and standing overnight, the precipitated solid was filtered off. The filtrate was evaporated to dryness. Chromatography on silica gel eluting with ethyl acetate-petroleum ether mixtures, gave the required phosphorane, initially as a foam, which crystallised from ether (5.70 g) m.p. 150°-6°. ν_(max) (CHCl₃) 1730, 1638, 1610 cm⁻¹.

EXAMPLE 5 Benzyl 6-(1-hydroxyethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR44## (i) 4-Allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoramylidenemethyl)-3-(1-hydroxyethyl)azetidin-2-one ##STR45##

A solution of N-isopropylcyclohexylamine (0.60 g) in dry tetrahydrofuran (10 ml) was stirred under argon and cooled to -78° C. This was treated with a 2.5 M solution of n-butyl lithium in n-hexane (1.70 ml). After ten minutes, a solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidin-2-one (9) (1.00 g) in dry tetrahydrofuran (10 ml) was added. Five minutes was allowed for the formation of the C(3) carbanion which was then quenched by the addition of acetaldehyde (0.54 ml). The mixture was stirred under argon for a further ten minutes before it was neutralized with acetic acid (0.56 g). The solvent was evaporated under reduced pressure and the residue chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate/cyclohexane mixtures grading from 1:1 to pure ethyl acetate. This gave a mixture of the cis and trans-isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxyethyl)azetidin-2-one (0.71 g; 65%) (20 ) and (21); ν_(max) (CHCl₃) 3000, 1735 and 1620 cm⁻¹.

(ii) Benzyl 6-(1-hydroxyethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR46##

A mixture of cis and trans-isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxyethyl)azetidin-2-one (0.79 g) as obtained in section (i) was dissolved in redistilled ethyl acetate (70 ml). An excess of trifluoroacetic acid (1.60 g) was added and the mixture cooled to -78° C. Ozone was passed into the reaction mixture until it was pale blue in colour. Argon was then bubbled through the solution until all the excess ozone had been removed. A solution of triphenylphosphine (0.37 g) in ethyl acetate was added and argon bubbled through the mixture for a further ten minutes. The reaction flask was then transferred to an ice bath and a saturated aqueous solution of sodium bicarbonate (104 ml) was added to generate the phosphoranes (22) and (23). The mixture was stirred vigourously under argon for thirty minutes. The ethyl acetate layer was separated, washed with brine and dried over sodium sulphate.

The solution was left to stand at room temperature for three days to allow the cyclisation reactions to proceed to completion. The ethyl acetate was then evaporated off under vacuum and the residue chromatographed on silica gel 60 (<230 mesh) (80 g), eluting with ethyl acetate/60°-80° petroleum ether mixtures grading from 3:7 to 7:3. Only two of the four possible diastereoisimers of benzyl 6-(1-hydroxyethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate could be isolated from the reaction mixture; these were one cis and one trans-isomer about the β-lactam ring. The pure cis-isomer (25) (0.030 g; 7.4%) was a crystalline material which could be recrystallised from ethyl acetate/60°-80° petroleum ether; m.p. 94°-99° C. ν_(max) (CHCl₃) 3000, 1775, 1725 and 1615 cm⁻¹ ; δ ppm ((CD₃)₂ CO) 7.22-7.40 (5H, m, phenyl), 6.46 (1H, t J 21/2 Hz, C3-H), 5.17 (2H, s, --CH₂ --Ph), 4.25 (1H, ddd J 10, 8 and 6 Hz, --C5--H) overlapping with 3.94-4.23 (1H, m side-chain --CH), 3.51 (1H, dd J 6 and 6 Hz, C6-H), 3.25 (1H, ddd J 18, 8 and 21/2 Hz, C4-H), 2.63 (1H, ddd J 18, 10 and 21/2 Hz, C4-H), 1.25 (3H, d J 6 Hz, --CH₃) (M⁺ at m/e 287.1150. C₁₆ H₁₇ NO₄ requires 287.1157).

The pure trans-isomer (24) (0.07 g; 17.4%) had ν_(max) (CHCl₃) 3000, 1780, 1725 and 1610 cm⁻¹ ; δ ppm ((CD₃)₂ CO) 7.2-7.5 (5H, m, phenyl), 6.36 (1H, t, J 21/2 Hz, C3-H), 5.17 (2H, s, --CH₂ --Ph), 4.20 (1H, td J 9 and 3 Hz, C5-H) overlapping with 3.94-4.23 (1H, m, side chain --CH), 3.31 (1H, dd J 31/2 and 3 Hz, C6-H), 2.96 (1H, s, --OH), 2.77 (2H, dd J 9 and 21/2 Hz, C4-H's), 1.25 (3H, d J 6 Hz, --CH₃) (M⁺ at m/e 287.1156. C₁₆ H₁₇ NO₄ requires 287.1157).

EXAMPLE 6 Benzyl 6-(1-hydroxy-1-phenylmethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR47## (i) 4-Allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxy-1-phenylmethyl)azetidin-2-one ##STR48##

A solution of N-isopropylcyclohexylamine (1.20 g) in dry tetrahydrofuran (20 ml) was stirred under argon and cooled to -78°. This was treated with a 1.6 M solution of n-butyl-lithium in n-hexane (5.30 ml). After ten minutes, a solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl) azetidin-2-one (9) (2.00 g) in dry tetrahydrofuran (40 ml) was added. Five minutes were allowed for the formation of the C(3) carbanion which was then quenched by the addition of benzaldehyde (1.0 ml). The solution was kept at -78° for a further ten minutes, and then it was allowed to warm to room temperature before being neutralised with acetic acid. The solvent was evaporated under reduced pressure, the residue chromatographed on silica gel 60 (<230 mesh), eluting with ethyl acetate/60°-80° petroleum ether mixtures grading from 1:1 to 3:1. This gave a mixture of the cis and trans isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidene methyl)-3-(1-hydroxy-1-phenylmethyl) azetidin-2-one (1.52 g, 63%) (26) and (27) ν_(max) (CHCl₃) 3400, 3000, 1725, 1615 cm⁻¹.

(ii) Benzyl 6-(1-hydroxy-1-phenylmethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR49##

A mixture of cis and trans-isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxy-1-phenylmethyl)azetidin-2-one (0.80 g) as obtained in section (i) was dissolved in ethyl acetate (40 ml). An excess of trifluoroacetic acid (1.50 g) was added and the mixture cooled to -78°. Ozone was passed into the reaction mixture until it was pale blue in colour. Argon was then bubbled through the solution until all the excess ozone had been removed. A solution of triphenylphosphine (0.34 g) in ethyl acetate was added and argon bubbled through the mixture for a further ten minutes. The reaction flask was allowed to warm to room temperature, and a saturated solution of sodium bicarbonate (20 ml) was added to generate the phosphoranes (28) and (29). Argon was passed through the mixture for thirty minutes. The ethyl acetate layer was separated, washed with brine, and dried over sodium sulphate.

The solution was left to stand at room temperature for three days to allow the cyclisation reactions to proceed to completion. The ethyl acetate layer was evaporated off under reduced pressure and the residue chromatographed on silica gel 60 (<230 mesh), eluting with 1:1 ethyl acetate/cyclohexane. Only two of the four possible diastereoisomers of benzyl 6-(1-hydroxy-1-phenylmethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate could be isolated from the reaction mixture; these were one cis and one trans isomer about the β-lactam ring. The pure cis-isomer (30) (0.12 g 27%) was a crystalline material which could be recrystallized from ethyl acetate/60°-80° petroleum ether; m.p. 124°; ν_(max) (CHCl₃) 3550, 3010, 1775, 1725 and 1610 cm⁻¹ ; δ ppm (C₆ D₆) 1.5-1.9 (1H, m, C4-H) 2.2-2.7 (2H, m, C4-H and OH), 3.2-3.7 (2H, m, C5 -H and C6-H), 4.43 (1H, dd, J 7 and 3 Hz, CH-O), 5.09 and 5.11 (2H, centre lines of ABq, benzyl CH₂), 6.12 (1H, t, J 3 Hz, C3-H) and 7.0-7.4 (10H, m, phenyls); λ_(max) (EtOH) 277 nm (ε 4830).

The pure trans-isomer (31) (0.12 g, 27%) had ν_(max) (CHCl₃) 3600-3400, 3020, 1175, 1715 and 1610 cm⁻¹, δ ppm (C₆ D₆) 1.89 (2H, dd, J 9 and 3 Hz, C4-H₂), 2.70 (1H, br, OH), 3.15 (1H, dd, J 5 and 3 Hz C6-H), 3.69 (1H, td, J 9 and 3 Hz, C5-H), 4.67 (1H, d, J 5 Hz, CH-O), 5.01 and 5.03 (2H, centre lines of ABq, benzyl CH₂), 5.90 (1H, t, J 3 Hz, C3-H) and 6.9-7.4 (10H, m, phenyls).

The β-lactamase inhibition (I₅₀) values in μg/ml for (30) were as follows:

    ______________________________________                                         Proteus mirabilis C889    0.27                                                 Staphylococcus aureus Russell                                                                            0.052                                                ______________________________________                                    

EXAMPLE 7 Benzyl 6-(1-hydroxycyclohex-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR50## (i) 4-Allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxycyclohex-1-yl)azetidin-2-one ##STR51##

A solution of N-isopropylcyclohexylamine (0.60 g) in dry tetrahydrofuran (5 ml) was cooled to -78° and stirred under an argon atmosphere. It was treated with a 1.6 M solution of n-butyl lithium in hexane (2.7 ml) and after 10 minutes a solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (9) (1.00 g) in dry tetrahydrofuran (15 ml) was added. The resulting red-brown solution was stirred for a further 10 minutes and then treated with cyclohexanone (0.40 ml). The reaction mixture was allowed to warm to about 0° to allow the reaction to go to completion; at which point the solution became pale yellow. It was neutralized with acetic acid (0.56 g.) and the solvent evaporated off under reduced pressure. The residue was partitioned between ethyl acetate and brine. The ethyl acetate solution was separated, dried over sodium sulphate and then concentrated. The residue was chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 1:1 grading to 7:3. This yielded a mixture of cis and trans-isomers of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxycyclohex-1-yl)azetidine-2-one (32) and (33) (0.76 g, 64%); ν_(max) (CHCl₃) 3400, 2980, 2920, 2850, 1735 and 1615 cm⁻¹.

(ii) Benzyl 6-(1-hydroxycyclohex-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR52##

A solution of the mixed isomers of 4-allyl-1-(benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-3-(1-hydroxyclohex-1-yl)azetidin-2-one (32) and (33) (0.75 g.) in ethyl acetate (50 ml) was treated with trifluoroacetic acid (2.0 ml). The solution was cooled to -78° and ozone passed through until the solution just became blue. The excess ozone was blown off in a stream of argon and a solution of triphenylphosphine (0.32 g) in ethyl acetate (5 ml) added. The passage of argon through the solution was continued for 30 minutes and then the reaction flask was transferred to an ice bath. Saturated aqueous sodium bicarbonate (60 ml) was added in one portion with vigorous stirring, to neutralize the reaction. After a further 30 mins. the ethyl acetate solution was separated, washed with brine, and dried over sodium sulphate. It was set aside overnight and the solution was then concentrated and chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 3:7 grading to 1:1. The first β-lactam containing compound to be eluted was the cis-isomer of benzyl 6-(1-hydroxycyclohex-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate (34) (0.04 g, 10%); m.p. 125°-126° (ethyl acetate/60°-80° petroleum ether); ν_(max) (CHCl₃) 3600, 3000, 2920, 2850, 1770, 1720 and 1615 cm⁻¹. λ_(max) (EtOH) 275 nm (ε 4240); τ (CDCl₃) 2.6-2.8 (5H, m, phenyl), 3.50 (1H, t, J 3 Hz, C3-H), 4.73 and 4.89 (2H, ABq, J 12 Hz, benzyl CH₂), 5.76 (1H, td, J 9 and 51/2 Hz, C5-H), 6.24 (1H, ddd, J 18, 9 and 3 Hz, C4-H), 6.39 (1H, d, J 51/2 Hz, C6-H), 7.42 (1H, ddd, J 18, 9 and 3 Hz, C4-H), 8.36 (1H, s, OH) and 8.1-8.8 (10H, m, cyclohexyl); (Found: C, 70.4; H, 6.8; N, 4.1%. C₂₀ H₂₃ NO₄ requires C, 70.4; H, 6.8 and N, 4.1%).

Further elution of the column gave the corresponding trans-isomer (35) (0.18 g, 43%); m.p. 102°-4° (ethyl acetate/60°-80° petroleum ether); ν_(max) (CHCl₃) 3550, 3000, 2920, 2850, 1775, 1725 and 1615 cm⁻¹ ; λ_(max) (EtOH) 279 nm (ε 4530); τ (CDCl₃) 2.6-2.8 (5H, m, phenyl), 3.61 (1H, t, J 21/2 Hz, C3-H), 4.71 and 4.87 (2H, ABq, J 12 Hz, benzyl CH₂), 5.76 (1H, td, J 8 and 3 Hz, C5-H), 6.78 (1H, d, J 3 Hz, C6-H), 7.09 (1H, ddd, J 18, 8 and 21/2 Hz, C4-H), 7.34 (1H, ddd, J 18, 8 and 21/2 Hz, C4-H), 8.25 (1H, s, OH) and 8.1-8.8 (10H, m, cyclohexyl); (Found: C, 70.4; H, 6.7; N, 4.0%. C₂₀ H₂₃ NO₄ requires C, 70.4; H, 6.8 and N, 4.1%).

The β-lactamase inhibition (I₅₀) values in μg/ml for (34) were as follows:

    ______________________________________                                         Enterobacter P99    5                                                          Pseudomonas aeruginosa A                                                                           1.4                                                        Esherichia coli JT 4                                                                               16                                                         Staph. aureus Russell                                                                              4.6                                                        ______________________________________                                    

EXAMPLE 8 Benzyl 6-benzyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR53## (i) 4-Allyl-3-benzyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one ##STR54##

A solution of N-isopropylcyclohexylamine (0.60 g) in dry tetrahydrofuran (5 ml) was stirred under argon and cooled to -78°. It was treated with a 1.6 M solution of n-butyl lithium in hexane (3.0 ml) and after 10 mins a solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (9) (1.00 g) in dry tetrahydrofuran (12 ml) was added to give a red solution. After a further 10 minutes the reaction mixture was treated with benzyl bromide (0.36 g) and 5 minutes later the reaction flask was removed from the cooling bath to allow the reaction to go to completion. It was neutralized with acetic acid (ca 0.5 g.) and then concentrated. Column chromatography on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 1:1 grading to 7:3 gave 4-allyl-3-benzyl-1-(1-benzyloxycarbonyl-1-triphenylphorphoranylidenemethyl)azetidine-2-one (36) (0.38 g, 32 %); ν_(max) (CHCl₃) 2980, 1730 and 1610 cm⁻¹. Continued elution resulted in recovery of the starting phosphorane (9) (0.42 g, 42%).

(ii) Benzyl 6-benzyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR55##

A solution of 4-allyl-3-benzyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (36) (0.38 g) in ethyl acetate (20 ml) was treated with trifluoroacetic acid (1.0 ml). The solution was cooled to -78° and ozone passed through it until it just became blue in colour. The excess ozone was blown off in a stream of argon and a solution of triphenylphosphine (0.16 g) in ethyl acetate (2 ml) was then added. The reaction solution was purged with argon for the next 30 minutes and the reaction flask was then transferred to an ice bath. Saturated aqueous sodium bicarbonate (30 ml) was added with vigorous stirring and after a further 30 minutes the ethyl acetate solution was separated, washed with brine and dried over sodium sulphate. Column chromatography on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 3:7 gave benzyl 6-benzyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate as the trans isomer (37) (0.09 g. 42%). It was a colourless gum; ν_(max) (CHCl₃) 3020, 2960, 1785, 1725 and 1610 cm⁻¹ ; τ (CDCl₃) 2.6-3.0 (10H, m, phenyls), 3.66 (1H, t, J 3 Hz, C3-H), 4.80 (2H, s, benzyl CH₂ -O), 6.02 (1H, td, J 81/2 and 3 Hz, C5-H), 6.60 (1H, ddd, J 9, 6 and 3 Hz, C6-H), 6.88 (1H, d, J 6 Hz, inner signal of ABX for PhCH₂ -C6), 6.97 (1H, d, J 9 Hz, inner signal of ABX for PhCH₂ -C6), 7.29 and 7.32 (2H, each a dd, J 81/2 and 3 Hz, inner signals of AB for C4-H₂).

EXAMPLE 9 Benzyl 6-methyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR56## (i) 4-Allyl-3-methyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one ##STR57##

A solution of N-isopropylcyclohexylamine (0.30 g) in dry tetrahydrofuran (5 ml) was stirred under argon and cooled to -78°. This was treated with a 2.5 M solution of n-butyl lithium in hexane (0.85 ml) and stirred for 10 minutes. A solution of 4-allyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (9) (0.50 g) in tetrahydrofuran (5 ml) was added and after 5 minutes the anion was quenched by addition of methyl iodide (0.12 ml). After a period of 10 minutes the reaction vessel was transferred to an ice bath and a further 10 minutes later the reaction was neutralized by addition of acetic acid (0.16 ml). The solvent was then stripped off and the residue partitioned between ethyl acetate and brine. The ethyl acetate solution was separated, washed with brine and dried over sodium sulphate. The product was subjected to careful column chromatography on silica gel 60 eluting with cyclohexane/ethyl acetate mixtures grading from 1:1 to 3:7. This gave 4-allyl-3-methyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (38) (0.10 g, 19%); ν_(max) (CHCl₃) 3000, 1735 and 1610 cm.⁻¹ Running closely behind this was recovered starting phosphorane (9) (0.17 g. 33%).

(ii) Benzyl 6-methyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR58##

A solution of 4allyl-3-methyl-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (38) (0.29 g) in ethyl acetate (25 ml) was treated with trifluoroacetic acid (0.4 ml) and then cooled to -78°. Ozone was bubbled through the solution until it just became pale blue in colour. The excess ozone was blown off in a stream of argon and an ethyl acetate solution of triphenylphosphine (0.14 g) was then added. After a further 10 minutes the reaction flask was transferred to an ice bath and saturated aqueous sodium bicarbonate (45 ml) was added with vigorous stirring. This was continued for 30 minutes and the ethyl acetate solution was then separated, washed with brine and dried over sodium sulphate. The solution was concentrated and chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether mixtures grading from 3:7 to 6:4. This gave the trans-isomer of benzyl 6-methyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene- 2-carboxylate (39) (0.08 g, 55%); ν_(max) (CHCl₃) 3000, 1780, 1725 and 1615 cm⁻¹ ; δppm ((CD₃)₂ CO) 1.34 (3H, d, J 7 Hz, CH₃), 2.85 (2H, dd, J 9 and 2 Hz, C4-H₂), 3.24 (1H, dq, J 3 and 7 Hz, C6-H), 3.91 (1H, dt, J 3 and 9 Hz, C5-H), 5.20 (2H, s, benzyl CH₂), 6.45 (1H, t, J 2 Hz, C3-H) and 7.2-7.5 (5H, m, phenyl); (M⁺ at m/e 257.1052 C₁₅ H₁₅ NO₃ requires 257.1051).

EXAMPLE 10 Phthalidyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR59## (i) Preparation of 7-(1-phthalidyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR60##

The azetidinone (1) (0.6 g), glyoxylic acid monohydrate (0.46 g), 4×4 A° molecular sieves (1/8" pellets), and dry DMF (3 ml) were stirred at room temperature for 5 hours. The mixture was cooled to 0° and potassium carbonate (0.345 g) was added. The mixture was allowed to warm up to room temperature and stirred for 5 minutes. Bromophthalide (1.07 g) was added and the mixture was stirred for 16 hours. The resulting solution was poured onto N/10 hydrochloric acid (25 ml) and ethyl acetate (25 ml). The organic layer was washed once more with N/10 hydrochloric acid (25 ml) and then with saturated aqueous sodium hydrogen carbonate (25 ml) and brine (25 ml); each aqueous washing being extracted once with ethyl acetate (25 ml). The combined organic layers were dried (Na₂ SO₄) and the solvent removed under reduced pressure to give a white solid (0.73 g).

A stirred solution of this solid in dry tetrahydrofuran (30 ml), under argon, was cooled to -20°, and treated with 2,6-lutidine (0.52 ml) followed by thionyl chloride (0.33 ml) in tetrahydrofuran (2 ml). After stirring for 20 minutes at -20° the mixture was brought to room temperature and filtered. The precipitated solid was washed with toluene and the combined flitrate and washings were evaporated to dryness under reduced pressure. The residue was dissolved in toluene and re-evaporated to dryness to remove excess thionyl chloride.

The oil obtained was dissolved in dry tetrahydrofuran (25 ml) and treated with 2,6-lutidine (0.52 ml) and triphenylphosphine (1.2 g). After stirring for 16 hours, the mixture was filtered and the filtrant washed with ethyl acetate (25 ml). The filtrate and washings were combined and the solvent removed under reduced pressure. The residue was dissolved in ethyl acetate (50 ml) and N/2 hydrochloric acid (25 ml). The organic layer was separated and the aqueous layer washed once with ethyl acetate (25 ml). The combined organic extracts were dried (Na₂ SO₄) and the solvent removed.

Chromatography on silica gel eluting with petroleum ether/ethyl acetate mixtures gave the phosphorane (40) which crystallised on addition of ether (0.9 g) m.p. 143°-5° (ethyl acetate/petroleum ether) having ν_(max) (CHCl₃) 1780, 1740, 1670 sh, and 1640 cm⁻¹. (Found: C, 73.4; H, 5.0; N, 2.3. C₃₅ H₂₈ NPO₅ requires C, 73.3; H, 4.9; N, 2.4%).

(ii) Preparation of Phthalidyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR61##

The phosphorane (40) (0.345 g) was dissolved in 5:1 ethyl acetate/trifluoroacetic acid (15 ml). The solution was left at room temperature for 10 minutes and then cooled to -70°. Ozone was then passed through the solution until it became pale blue. Argon was passed through the solution to remove excess ozone and then triphenylphosphine (0.2 g) in ethyl acetate (2 ml) was added. The mixture was warmed up to 0° with an ice bath and then saturated sodium hydrogen carbonate solution (50 ml) was added carefully with vigorous agitation. The layers were separated and the aqueous layer extracted once more with ethyl acetate (25 ml). The combined organic layers were dried (Na₂ SO₄), filtered and allowed to stand at room temperature for 3 hours. Methoxycarbonylmethylenetriphenylphosphorane (0.21 g) was added to the solution dissolved in ethyl acetate and left for 1 hour. The solution was evaporated to dryness. Rapid chromatography on silica/hyflo eluting with 1:1 ethyl acetate/petroleum ether followed by slower chromatography on silica gel eluting with 1:1 ethyl acetate/petroleum ether gave the phthalide ester (41) (0.084 g) as a white solid, m.p. 140°-5° (ethyl acetate/petroleum ether) having ν_(max) (CHCl₃) 1795, 1745, 1725, 1665, 1615 and 980 cm⁻¹. δ(CDCl₃) 2.4-2.9 (4H, m, methylenes), 3.70 (3H, s, CH₃), 3.6-3.9 (1H, m, C4-H), 4.4 (1H, m, C5-H), 5.8 (1H, br.d, J 16 Hz, MeO₂ C--CH═), 6.50 and 6.62 (1H, 2×t, J 3 Hz, C3-H in two isomers), 6.85 (1H, dt, J 6, 16 Hz, MeO₂ CCH═CH--), 7.41 and 7.47 (1H, 2×s, phthalide methines), and 7.55-7.95 (4H, m, aromatic), λ_(max) (EtOH) 208, 274 (ε6,900), and 280 (ε6,700) nm. (Found: C, 62.0; H, 4.4; N, 3.6. C₂₀ H₁₇ NO₇. 1/4H₂ O requires C, 62.0; H, 4.5; N, 3.6%).

The concentrations of this compound required to inhibit the growth of the following bacteria are given below.

    ______________________________________                                         Organism            μg/ml (agar)                                            ______________________________________                                         B. subtilis A       25                                                         E. coli 0111        50                                                         Klebsiella aerogenes A                                                                             50                                                         Proteus mirabilis C977                                                                             100                                                        Salmonella typhimurium CT 10                                                                       50                                                         Shigella sonnei MB 11967                                                                           50                                                         Staph. aureus Oxford                                                                               ≦0.8                                                Staph. aureus Russell                                                                              ≦0.8                                                Staph. aureus 1517  ≦0.8                                                Staph. pyogenes CN 10                                                                              ≦0.8                                                ______________________________________                                    

EXAMPLE 11 Phthalimidomethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR62## (i) Preparation of 7-(1-Hydroxy-1-phthalimidomethylcarbonylmethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR63##

The azetidinone (1) (0.6 g), glyoxylic acid monohydrate (0.48 g), 6×4 A° molecular sieves (1/8" pellets), and dry DMF (3 ml) were stirred at room temperature for 5 hours. Potassium carbonate (0.365 g) was added followed by phthalimidomethyl bromide (1.25 g) and the mixture was stirred for 16 hours. The resulting solution was poured onto ethyl acetate (25 ml) and N/10 hydrochloric acid (25 ml). The organic layer was washed with saturated sodium hydrogen carbonate (25 ml) and brine, each aqueous washing being extracted once with ethyl acetate (25 ml). Drying (MgSO₄) and removal of solvent from the combined extracts followed by chromatography on silica gel (eluted with ethyl acetate/petroleum ether mixtures) gave the alcohols (42) (0.91 g) as a white solid. The alcohols can be separated by more careful chromatography. Isomer I m.p. 132-4 (ethyl acetate/petroleum ether) has ν_(max) (CHCl₃) 1790, 1735, 1670 and 1390 cm⁻¹, δ(CDCl₃) 1.85-2.75 (4H, m, allylic CH₂) 3.27 (1H, m, β-lactam H), 4.05 (1H, m, β-lactam H), 4.37 (1H, d, J 7 Hz, OH), 5.38 (1H, d, J 7 Hz, CHOH), 5.77 (4H, m, olefinic and --CH₂ --N), and 7.76 (4H, m, aromatic). (Found: C, 60.5; H, 4.75; N, 7.75. C₁₈ H₁₆ N₂ O₆ requires C, 60.7; H, 4.5; N, 7.85%), and Isomer II m.p. 145 (ethyl acetate/petroleum ether) has δ(CDCl₃) 1.85-2.6 (4H, m, allylic CH₂) 3.29 (1H, m, β-lactam H), 4.14 (1H, m, β-lactam H), 4.71 (1H, br, OH), 5.36 (1H, br, CH-OH), 5.67 (2H, m, olefinic), 5.73 (2H, s, --CH₂ --N), and 7.77 (4H, m, aromatic). (Found: C, 60.8; H, 4.20; N, 7.75. C₁₈ H₁₆ N₂ O₆ requires C, 60.7; H, 4.5; N, 7.85%).

(ii) Preparation of 7-(1-Phthalimidomethoxycarbonyl-1-triphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR64##

A stirred solution of the alcohols (42) (0.91 g) in dry tetrahydrofuran (20 ml) under argon, was cooled to -20°, and treated with 2,6-lutidine (0.59 ml) followed by thionyl chloride (0.366 ml) in tetrahydrofuran (3 ml). After stirring for 20 minutes at -20° the mixture was brought to room temperature and filtered. The precipitated solid was washed with toluene and the combined filtrate and washings were evaporated to dryness. The residue was dissolved in toluene and re-evaporated to remove the thionyl chloride.

The oil obtained was dissolved in dry tetrahydrofuran (20 ml) and treated with 2,6-lutidine (0.59 ml) and triphenylphosphine (1.33 g). After stirring for 16 hours, the mixture was filtered and the solvent removed from the filtrate. Chromatography on silica gel eluting with petroleum ether/ethyl acetate gave the phosphorane (43), which crystallised on addition of ether; (1.23 g), having ν_(max) (CHCl₃) 1790, 1735 and 1625 cm³¹ 1.

(iii) Preparation of Phthalimidomethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR65##

The phosporane (43) (0.24 g) was dissolved in ethyl acetate (10 ml) and trifluoroacetic acid (0.32 ml) was added. The reaction mixture was cooled to -70° and ozone was bubbled in until the solution became pale blue. Argon was passed through the solution to remove excess ozone and then triphenylphosphine (0.16 g) in ethyl acetate (2 ml) was added. The mixture was warmed up to 0° with an ice bath and then saturated sodium hydrogen carbonate (10 ml) was added with vigorous agitation. After 1 hour at room temperature, the layers were separated and methoxycarbonylmethylenetriphenylphosphorane (0.14 g) was added to the ethyl acetate layer. After one hour the solvent was removed and the resulting oil initially purified by chromatography on silica eluted with petroleum ether/ethyl acetate. Further purification using a thick silica plate eluted with ethyl acetate gave the ester (44) (0.05 g) as a white solid m.p. 132-137 having ν_(max) (CHCl₃) 1790, 1740, 1660 and 1620 cm⁻¹. δ(CDCl₃) 2.4-2.8 (4H, m, methylene), 3.5-3.85 (1H, m, C6-H), 3.7 (3H, s, CH₃), 4.35 (1H, dt, J 6, 9 Hz, C5-H), 5.65-5.95 (3H, m, MeO₂ CCH═ and OCH₂ N), 6.46 (1H, t, J 3 Hz, C3-H), 6.83 (1H, dt, J 7, 16 Hz, MeO₂ CCH═CH--), and 7.6-7.95 (4H, m, aromatic). (Found: C, 60.1; H, 4.5; N, 6.65. C₂₁ H₁₈ N₂ O₇.1/2H₂ O requires C, 60.1; H, 4.55; N, 6.70%).

EXAMPLE 12 Phthalidyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR66## (i) Preparation of 7-(1-phthalidyloxycarbonyl-1-tris-p-methoxyphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR67##

The phosporane (45) was prepared as in Example 10 (i) except that tris-p-methoxyphenylphosphine (1.2 g) was used instead of triphenylphosphine. Chromatography gave the phosphorane (45) (0.71 g) m.p. 194-6 (ethyl acetate/petroleum ether) having ν_(max) (CHCl₃) 1780, 1745, 1650, 1600, 1265 and 1115 cm⁻¹ (Found: C, 67.35; H, 5.0; N, 1.8. C₃₈ H₃₄ PNO₈.H₂ O requires C, 66.95; H, 5.3; N, 2.0%).

(ii) Preparation of 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR68##

The phosphorane (45) (0.133 g) was dissolved in 5:1 ethyl acetate/trifluoroacetic acid (6 ml). The solution was left at room temperature for 10 minutes and then cooled to -70°. Ozone was then passed through the solution until it became pale blue and excess ozone removed with argon. Tris-p-methoxyphenylphosphine (0.07 g) in ethyl acetate (1 ml) was added and the solution was warmed up to 0° with an ice bath. Saturated aqueous potassium hydrogen carbonate (5 ml) was added carefully with vigorous agitation and the layers were separated. The aqueous layer was washed twice with ethyl acetate (5 ml) and the combined organic layers dried (MgSO₄). This solution was heated at 45° for 3/4 hour and then the solvent was removed under reduced pressure. Rapid chromatography on silica eluting with 1:1 petroleum ether/ethyl acetate gave the aldehyde (46) (0.02 g) as a white solid after trituration with ether having ν_(max) (CHCl₃) 2950, 1795, 1740, 1610 and 980 cm⁻¹ and n.m.r. having δ9.17 (s, aldehyde C-H).

EXAMPLE 13 Phthalidyl 6-(4-oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR69## (i) Preparation of Acetonyltris-p-methoxyphenylphosphonium chloride ##STR70##

A solution of tris-p-methoxyphenylphosphine (2.66 g) and chloroacetone (0.65 g) in chloroform (6 ml) was heated under reflux for 45 minutes. The solution was poured into ether (60 ml) and the solid collected. The chloride (47) had ν_(max) (KBr) 2800, 1710, 1595, and 1270 cm⁻¹. λ_(max) (EtOH) 212 (ε37,100) and 247 (ε45,800) nm, δ(CDCl₃) 2.48 (3H, d, J 2 Hz, COCH₃), 3.88 (9H, s, OCH₃), 5.77 (2H, d, J 11 Hz, CH₂), and 6.95-8.0 (12H, m, aromatic).

(ii) Preparation of Acetylmethylenetris-p-methoxyphenylphosphorane ##STR71##

Sodium carbonate (0.053 g) in water (5 ml) was added to a suspension of the chloride (47) (0.445 g) in benzene (5 ml). After stirring for 5 minutes, the organic layer was separated, dried (MgSO₄) and the benzene was removed under reduced pressure. The resulting oil crystallised from ether/cyclohexane and had m.p. 148.5-149 (ethyl acetate/petroleum ether), δ(CDCl₃) 2.07 (3H, d, J 2 Hz, COCH₃), 3.83 (10H, s, obscuring br.s, ═CH and OCH₃) and 6.85-7.75 (12H, m, aromatics)(Found: C, 70.44; H, 6.25; C₂₄ H₂₅ PO₄ requires C, 70.59; H, 6.15%).

(iii) Preparation of Phthalidyl 6-(4-oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR72##

The phosphorane (45) (0.4 g) [as prepared in Example 12(i)] was dissolved in 5:1 ethyl acetate-trifluoroacetic acid (18 ml). The solution was left at room temperature for 10 minutes and then cooled to -70°. Ozone was then passed through the solution until it became pale blue. Argon was passed through the solution to remove excess ozone and then tris-p-methoxyphenylphosphine (0.2 g) in ethyl acetate (2 ml) was added. The mixture was warmed up to 0° with an ice bath and then saturated potassium hydrogen carbonate (15 ml) was added carefully with vigorous agitation. The layers were separated and the aqueous layer extracted twice more with ethyl acetate (25 ml). The combined organic layers were dried (MgSO₄), filtered and then heated for 15 minutes at 50°. Acetylmethylenetris-p-methoxyphenylphosphorane (0.2 g) was added, and the solution heated at 50° for 11/2 hour and then left overnight at room temperature. Chromatography on silica eluting with ethyl acetate-petroleum ether mixtures gave the ketone (49) (0.015 g) as an oil having ν_(max) (CHCl₃) 1795, 1750, 1680, 1635, 1615 and 985 cm⁻¹, δ(CDCl₃) 1.8-3.0 (4H, m, methylenes), 2.23 (3H, s, CH₃), 3.75 (1H, m, C6-H), 4.41 (1H, m, C5-H), 6.02 (1H, br.d, J 16 Hz, CH₃ COCH═), 6.4-6.9 (2H, m, C3-H and --CH═CH--COCH₃), 7.40 and 7.46 (1H, 2×s, phthalidyl methine), and 7.5-7.95 (4H, m aromatic).

EXAMPLE 14 Pivaloyloxymethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR73## (i) 7-(1-Pivaloyloxymethyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR74##

The azetidin-2-one (1) (0.4 g) in dimethylformamide (2 ml) was stirred with glyoxylic acid monohydrate (0.32 g) and 4 A type molecular sieves (4 chips) for 5 hours. Potassium carbonate (0.248 g) was added followed by pivaloyloxymethyl bromide (1.2 g). After stirring overnight the solution was diluted with ethyl acetate, washed with water, dried (MgSO₄) and evaporated. The residual oil (0.8 g) was chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate-petroleum ether (60°-80°) to give the alcohol (50), as a mixture of isomers, ν_(max) (CHCl₃) 3460, 3300, 1755 (b) cm⁻¹.

This mixture (0.26 g) in tetrahydrofuran (3 ml) was cooled to -20° and 2,6-lutidine (0.21 ml) followed by thionyl chloride (0.14 ml) were added with stirring. After 0.5 hours the reaction mixture was filtered, and the filtrate evaporated to dryness from toluene. The residue was dissolved in dioxan (2 ml). Triphenylphosphine (0.45 g) and 2,6-lutidine (0.21 ml) were added and the reaction stirred overnight at room temperature. The mixture was filtered, the filtrate evaporated and chromatographed on silica gel 60 (<230 mesh) to give the phosphorane (51) as a foam (0.291 g), ν_(max) (CHCl₃) 1740, 1630 cm⁻¹.

(ii) Pivaloyloxymethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR75##

The phosphorane (51) (0.1 g) was dissolved in ethyl acetate (5 ml) and trifluoroacetic acid (1 ml) at room temperature. The solution was cooled (-70°) and treated with ozone until the reaction solution showed a slight blue colouration. Argon was blown through the solution to remove excess ozone and then triphenylphosphine (0.075 g) dissolved in ethyl acetate was added. After five minutes the reaction vessel was transferred to an icebath and saturated sodium hydrogen carbonate solution (30 ml) was added with vigorous stirring. The ethyl acetate layer was separated, dried (MgSO₄), and kept for 45 minutes at room temperature. Methoxycarbonylmethylenetriphenylphosphorane (0.075 g) in the minimum volume of methylene chloride was added to the ethyl acetate solution. After one hour the solvent was removed and the residue chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate-petroleum ether (60°-80°) to give the product (52) (25 mg), m.p. 110°-112° (from ether), ν_(max) (EtOH) 210 and 275 nm (δ4060), ν_(max) (CHCl₃) 1785, 1750, 1725, 1660, 1610 cm⁻¹. δppm (CDCl₃) 1.22 (9H, s, Bu^(t)), 2.75 (2H, dd, J 9, 3 Hz, C4-H₂), 2.40-2.90 (2H, m, CH₂), 3.70 (3H, s, OMe), 3.65-3.90 (1H, m, C6-H), 4.40 (1H, dt, J 6, 9 Hz, C5-H), 5.81 (1H, dd, J_(t) 15, 1 Hz, MeO₂ C--CH═CHCH₂), 5.81 and 5.84 (2H, inner signals ABq, CO₂ CH₂ O), 6.54 (1H, t, J 3 Hz, C3-H), 6.86 (1H, dt, J 6, 15 Hz, MeO₂ C--CH═CHCH₂).(Found: C, 59.2; H, 6.4; N, 3.8%; M, 365.1498. C₁₈ H₂₃ NO₇ requires C, 59.2; H, 6.3; N, 3.8%. M, 365.1475). The concentrations of this compound required to inhibit the growth of the following bacteria are given below:

    ______________________________________                                         Organism            μg/ml (agar)                                            ______________________________________                                         B. subtilis A       20                                                         E. coli 0111        20                                                         Klebsiella aerogenes A                                                                             20                                                         Salmonella typhimurium CT 10                                                                       20                                                         Shigella sonnei MB 11967                                                                           20                                                         Staph. aureus Oxford                                                                                2                                                         Staph. aureus Russell                                                                               2                                                         Staph. aureus 1517   2                                                         ______________________________________                                    

EXAMPLE 15 p-Nitrobenzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR76## (i) 7-(1-Hydroxy-1-p-nitrobenzyloxycarbonylmethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR77##

p-Nitrobenzyl glyoxylate hydrate (9.08 g) was refluxed in benzene (150 ml) with provision for the removal of water. After 1 hour 8-oxo-7-azabicyclo [4.2.0]oct-3-ene (1) (2.46 g) was added and refluxing continued for 3.5 hours. The cooled solution was washed with water (x2), then brine. After back extraction of the first aqueous extract with ethyl acetate, the organic solutions were dried over magnesium sulphate, filtered combined, and evaporated. Chromatography on silica, eluting with ethyl acetate-petroleum ether mixtures gave two separate isomers of the alcohol (54) (43%). Less polar isomer I m.p. 153°-5° (crystalline plates ex ethyl acetate/ether). ν_(max) (CHCl₃) 3400 (broad), 1760, 1745, 1520, 1350 cm⁻¹. δppm (CDCl₃) 1.90-2.83 (4H, m, 2-CH₂), 3.23-3.55 (1H, m, β-lactam proton), 4.00-4.20 (1H, m, β-lactam) proton), 4.27 (1H, d, J 8 Hz, exchangeable with D₂ O, OH), 5.33 (2H, s, CH₂ Ar)obscuring 1H, CHOH; 5.67-5.88 (2H, m, CH═CH), 7.55 (2H, d, J 8.5 Hz, Ar), 8.23 (2H, d, J 8.5 Hz, Ar) (Found: C, 58.07; H, 5.15; N, 8.51%, C₁₆ H₁₆ N₂ O₆ requires C, 57.83; H, 4.85; N, 8.43%). More polar isomer II m.p. 118°-120° (fine crystalline needles ex ethyl acetate/ether). ν_(max) (CHCl₃) 3400 (broad), 1760-1745, 1520, 1350 cm⁻¹. δ ppm (CDCl₃) 1.83-2.77 (4H, m, 2-CH₂), 3.25-3.55 (1H, m, β-lactam proton), 4.02-4.37 (2H, m, β-lactam proton and CHOH, --OH exchangeable with D₂ O), 5.31-5.98 [5H, 5.35 (2H, s, CH₂ Ar), obscuring, 1H, which sharpens to s, at δ 5.40 on D₂ O exchange, CHOH, and 2H, m, CH═CH], 7.56 (2H, d, J 8 Hz, Ar), 8.23 (2H, d, J 8 Hz, Ar) (Found: C, 57.95; H, 4.95; N, 8.50%. C₁₆ H₁₆ N₂ O₆ requires C, 57.83; H, 4.85; N, 8.43%).

(ii) 7-(1-p-Nitrobenzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR78##

The alcohol (54), as a mixture of isomers, (1.86 g) in dry tetrahydrofuran (60 ml), under argon, was treated with lutidine (1.37 ml). To the solution, cooled to -20°, was added dropwise, with stirring, a solution of thionyl chloride (0.87 ml) in tetrahydrofuran (20 ml). A white solid came out of solution. The stirred mixture was allowed to reach room temperature over 20 minutes and was filtered and evaporated to dryness. The residue in dry dioxan (60 ml) was treated with triphenylphosphine (3.12 g) and lutidine (1.37 ml) and left stirring overnight at room temperature. The lutidine hydrochloride was separated by filtration, and the filtrate evaporated. The residue was taken up in ethyl acetate, washed with, water containing a few drops of hydrochloric acid, water then brine, dried over magnesium sulphate, filtered and evaporated. Chromatography on silica, eluting with ethyl acetate/petroleum ether mixtures gave the phosphorane (55, 2.68 g) as an amorphous solid. ν_(max) (CHCl₃) 1738, 1620 (shoulder), 1605, 1520, 1350 cm.sup. -1.

(iii) p-Nitrobenzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate ##STR79##

The phosphorane (55) (0.4 g) in ethyl acetate (30 ml) was treated with trifluoroacetic acid (1.61 ml). The solution was cooled (-70°) and treated with ozone until pale blue. Argon was blown through the solution to remove excess ozone, and then triphenylphosphine (0.272 mg) dissolved in ethyl acetate (5 ml) was added. After five minutes the reaction was transferred to an ice-bath and stirred vigorously with saturated aqueous sodium bicarbonate (30 ml), for 10 minutes. The organic phase was separated, dried over magnesium sulphate and filtered. The pale solution was stood at room temperature for 1.25 hours, then reduced to 15 ml by evaporation, and treated with carbomethoxymethylene triphenylphosphorane (0.26 g). After 30 minutes the solution was evaporated. Rapid chromatography of the residue on 4 g silica, eluting with ethyl acetate/petroleum ether mixtures gave the trans (about the C6-double bond) isomer (53a) (132 mg) m.p. 156°-9° (ex. ethyl acetate/petroleum ether), λ_(max) (ethanol) 269 nm (ε 14,300); ν_(max) (CHCl₃) 1782, 1722, 1655 (weak), 1605 (weak), 1525, 1350 cm⁻¹. δ ppm (CDCl₃) 2.73 (2H, dd, J 9.5, 3 Hz, C4-H), partially obscuring 2.25-2.90 (2H, m, side-chain CH₂), 3.69 (3H, s, CH₃), partially obscuring 3.74 (1H, td, J 9.5, 6 Hz, C5-H) 4.39 (1H, td, J 9.5, 6 Hz, C6-H), 5.20 and 5.42 (2H, ABq, J 14 Hz, CH₂ Ar), 5.80 (1H, d, J 16 Hz, trans CH═CHCH₂), 6.53 (1H, t, J 3 Hz, C3-H), 6.85 (1H, td, J 6, 16 Hz, trans CH═CHCH₂), 7.52 (2H, d, J 8 Hz, Ar), 8.14 (2H, d, J 8 Hz, Ar); (Found: C, 58.90; H, 4.70; N, 7.08. C₁₉ H₁₈ N₂ O₇ requires C, 59.06; H, 4.70; N, 7.25%).

The concentrations of this compound required to inhibit the growth of the following bacteria are given below.

    ______________________________________                                         Organism         μg/ml (agar)                                               ______________________________________                                         Staph. aureus Russell                                                                           2.46                                                          Strep. pneumoniae                                                                               7.4                                                           Strep. pyogenes  0.8                                                           ______________________________________                                    

A small amount (4 mg) of the cis isomer (53b) was also obtained m.p. 109°-111° (ex ether) λ_(max) (ethanol) 269 nm (ε 13,950), ν_(max) (CHCl₃) 1778, 1720, 1650 (weak), 1520, 1350 cm⁻¹. δ ppm (CDCl₃) 2.40-3.50 (4H, m, 2-CH₂), 3.66 (3H, s, CH₃), partially obscuring, 3.73 (1H, td, J 8 Hz, 6 Hz, C6-H), 4.35 (1H, td, J 9.5, 6 Hz, C5-H), 5.19 and 5.40 (2H, ABq, J 14 Hz, CH₂ Ar), 5.84 (1H, d, J 11 Hz, cis CH═CHCH₂), 6.22 (1H, ddd, J 11, 8.6 Hz, cis CH═CHCH₂), 6.55 (1H, t, J 3 Hz, C3-H), 7.52 (2H, d, J 8 Hz, Ar), 8.14 (2H d, J 8 Hz, Ar).

EXAMPLE 16 Benzyl 6-(3-cyano-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylat ##STR80##

The phosphorane (3) (1 g) was dissolved in ethyl acetate (50 ml) and treated with trifluoroacetic acid (1.25 ml). After five minutes at room temperature the reaction mixture was cooled to -70° C. Ozone was blown into the solution until it was pale blue. The excess ozone was then removed with a stream of argon. Triphenylphosphine (0.5 g) in ethyl acetate was added. After five minutes the mixture was transferred to an ice-bath and saturated sodium hydrogen carbonate solution (40 ml) was added with vigorous agitation. The organic phase was separated dried (MgSO₄) and treated with cyanomethylenetriphenylphosphorane (0.55 g) with stirring. After 40 minutes at room temperature the solution was evaporated to dryness and chromatographed on silica gel 60 (<230 mesh) eluting with 3:7 ethyl acetate: 60°-80° petroleum ether to give (56) (0.054 g of pure product obtained followed by 0.183 g contaminated with some triphenylphosphine oxide) showing ν_(max) (CHCl₃) 2250 (CN), 1785, 1730, 1640, 1620 cm⁻¹. δ ppm (CDCl₃) 2.45-2.90 (2H, m, CH₂), 2.73 (2H, dd, J 9, 3 Hz, C4-H₂), 3.60-3.90 (1H, m, C6-H), 4.40 (1H, dt, J 9, 6 Hz, C5-H), 5.25 (2H, s, CH₂), 5.40 (1H, dd, J 16, 1 Hz), 6.53 (1H, t, J 3 Hz), 6.60 (1H, dt, J 16, 7 Hz), 7.30 (5H, s, Ar). (Found: M, 308.1120. C₁₈ H₁₆ N₂ O₃ requires M, 308.1161).

The concentrations of this compound required to inhibit the growth of the following bacteria are given below.

    ______________________________________                                         Organism           μg/ml (agar)                                             ______________________________________                                         B. subtilis A      20                                                          Citrobacter freundii E8                                                                           20                                                          Enterobacter cloacae N1                                                                           20                                                          E. coli 0111       20                                                          Klebsiella aerogenes A                                                                            20                                                          Proteus mirabilis C977                                                                            20                                                          Proteus morganii I 580                                                                            20                                                          Proteus rettgeri WM16                                                                             20                                                          Salmonella typhimurium CT10                                                                       20                                                          Serratia marcescens US20                                                                          20                                                          Shigella sonnei MB 11967                                                                          20                                                          Staph. aureus Oxford                                                                              ≦2                                                   Staph. aureus Russell                                                                             ≦2                                                   Staph. aureus 1517 ≦2                                                   ______________________________________                                    

EXAMPLE 17 Benzyl 6-(4-Oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR81##

The phosphorane (3) (1 g) was dissolved in ethyl acetate (50 ml) and trifluoroacetic (1.25 ml). After cooling to -70° ozone was bubbled into the solution until it was pale blue. Excess ozone was then removed with a stream of argon and triphenylphosphine (0.5 g) in ethyl acetate (10 ml) was added. After five minutes the solution was transferred to an ice bath and neutralized with saturated sodium bicarbonate solution (40 ml) with vigorous agitation. The organic phase was separated, dried (MgSO₄) filtered and the solution made up to 100 ml with ethyl acetate. An aliquot of this solution (50 ml) containing the aldehyde (4) was treated with acetylmethylenetriphenylphosphorane (0.295 g) with stirring. The reaction solution was left at room temperature overnight (18h). The ethyl acetate was evaporated under reduced pressure and the residue rapidly chromatographed on silica gel 60 (15 g) (<230 mesh) eluting initially with 3:7 ethyl acetate: 60°-80° petroleum ether and then 1:1 ethyl acetate:petroleum ether. The product (57) was contaminated with triphenylphosphine oxide and therefore rechromatographed to give pure (57) (0.05 g) as a gum, ν_(max) (CHCl₃) 1785, 1730, 1680, 1630, 1620 cm⁻¹. δ ppm (CDCl₃) 2.25 (3H, s, COCH₃), 2.50-3.00 (4H, m, 2×CH₂), 2.55-3.95 (1H, m, C6-H), 4.40 (1H, dt, J 9 m 6 Hzm C5-H), 5.25 (2H, s), 6.15 (1H, d, J 16 Hz), 6.50 (1H, t, J 3 Hz, C3-H), 6.75 (1H, dt, J 16, 7 Hz), 7.30 (5H, s, Ar). (Found: M, 325.1345. C₁₉ H₁₉ NO₄ requires M, 325.1376).

EXAMPLE 18 p-Bromophenacyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR82## (i) 7-(1-Hydroxy-1-p-bromophenacyloxycarbonylmethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR83##

The azetidinone (1) (0.4 g) in anhydrous dimethylformamide (2 ml) was stirred with glyoxylic acid hydrate (0.32 g) in the presence of hexamethylphosphorictriamide (0.1 ml) and molecular sieves (3A; 4 pieces) for 5 h. Potassium carbonate (0.226 g) was added, and the solution stirred until effervescence had ceased (5 min.). p-Bromophenylbromide (1.00 g; 1.05 equiv.) in dimethylformamide (1.0 ml) and hexamethylphosphorictriamide (0.25 ml) was added, and the solution stirred overnight. The solution was diluted with ethyl acetate, washed with saturated aqueous sodium chloride solution (×3), dried (Na₂ SO₄) and evaporated to give a gum (1.9 g) which was chromatographed on Kieselgel. Elution of the column with ethyl acetate-petroleum ether (1:1) gave the glyoxylate ester (58). Isomer I as a foam, which slowly crystallised (ethyl acetate-petroleum ether) as needles (0.60 g), (47%) m.p. 135°-136°, ν_(max) (CHCl₃) 3250br, 1760sh, 1750, 1710, 1590, 970 cm⁻¹ ; δ (d₆ DMSO) 1.9-2.8 (4H, m), 3.35 (1H, m), 4.17 (1H, m) 5.51 (1H, d, J 6.5 Hz; sharpens to a singlet on D₂ O exchange) 5.55 (2H, s, phenacyl CH₂), 5.72br (2H, s), 6.81 (1H, d, J 6.5H, D₂ O exchangeable), 7.75 (2H, d, J 9 Hz) and 7.90 (2H, d, J 9 Hz) (Found: C, 51.9; H, 4.2; N, 3.6; Br, 20.00. C₁₇ H₁₆ BrNO₅ requires C, 51.8; H, 4.1; N, 3.6; Br, 20.3%).

Continued elution of the column gave the more polar Isomer II, which crystallised (ethyl acetate-petroleum ether) as platelets (0.55 g) (43%), m.p. 144°-146°, ν_(max) (CHCl₃) 3200br, 1760sh, 1750, 1710, 1590, 965 cm⁻¹ ; δ (d₆ DMSO) 1.9-2.8 (4H, m), 3.33 (1H, m) 4.15 (1H, m), 5.47 (1H, d, sharpens to a singlet on D₂ O exchange), 5.51 (2H, s, phenacyl CH₂), 5.71br (2H, s), 6.90 (1H, d, J 7 Hz, D₂ O exchangeable), 7.73 (2H, d, J 9 Hz), and 7.91 (2H, d, J 9 Hz). (Found: C, 51.7; H, 4.3; N, 3.3; Br, 20.6. C₁₇ H₁₆ BrNO₅ requires C, 51.8; H, 4.1; N, 3.6; Br, 20.3%).

(ii) 7-(1-p-bromophenacyloxycarbonyl-1-triphenylphorphoranylidenemethyl)-8-oxo-7-azabicyclo[4,2,0]oct-3-ene ##STR84##

The glyoxylate p-bromophenacyl ester (58) (0.383 g; 1:1 isomer ratio) in THF (8 ml) was treated with lutidine (230 μl), followed by thionyl chloride (139 μl) at -20° for 3.5 h. The material was rapidly filtered through celite, washed with ethyl acetate, and the filtrate and washings evaporated in vacuo. The residue in dioxan (4 ml, anhydrous) was treated with triphenylphosphine (0.51 g) and lutidine (230 μl) at room temperature overnight. Chromatography on Kieselgel (elution with ethyl acetate petroleum ether, 7:3) gave the phosphorane (59) as a gum (0.536 g) which crystallised from ethyl acetate-ether-petroleum ether as small rods (0,499 g.) (80%) m.p. 200°-202°, ν_(max) (CHCl₃) 1740st, 1710, 1620, 1590, 1480 cm⁻¹. (Found: C, 65.7; H, 4.7; N, 2.0; Br, 12.1. C₃₅ H₂₉ BrNO₄ P requires C, 65.8; H, 4.6; N, 2.2; Br, 12.5%).

(iii) p-Bromophenacyl-6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR85##

The phosphorane (59) (0.104 g) was converted to the bicyclic ester (60) and isolated by the method described for the benzyl ester in example 2. The product (60) (35 mg) crystallized from ethyl acetate-petroleum ester and had m.p. 134°-136°, ν_(max) 1785, 1725sh, 1715, 1700, 1660, 1610, 1590 cm⁻¹ ; λ_(max) (EtOH) infl 275, 258 (ε 21900), 210 (26,000); δ (CDCl₃) 2.45-2.9 (2H, m, C6 side-chain CH₂), 2.74 (2H, dd, J 9, 3 Hz, C4-H₂), 3.68 (3H, s), 3.6-3.9 (1H, m, C₆ -H), 4.40 (1H, dt, J 9, 6 Hz, C5-H), 5.36 (2H, s), 5.80 (1H, dt, J 15, 1 Hz), 6.60 (1H, t, J 3 Hz, C3-H), 6.86 (1H, dt, J 15, 6 Hz), 7.55 (2H, d, J 9 Hz) and 7.74 (2H, d, J 9 Hz). (Found: C, 53.4; H, 4.1; N, 3.2; Br, 17.9. C₂₀ H₁₈ BrNO₆ requires C, 53.6; H, 4.0; N, 3.1; Br, 17.8%).

EXAMPLE 19 Phthalidyl 6-(3-cyano-2-propen-1-yl)-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylat ##STR86##

The phosphorane (40) (0.345 g) was dissolved in 5:1 ethyl acetate/trifluoroacetic acid (15 ml) and the solution left at room temperature for 15 minutes. The solution was then cooled (-70°) and ozone passed through the solution until it became slight blue. Argon was passed through the solution to remove excess ozone and triphenylphosphine (0.2 g) in ethyl acetate (10 ml) was added. The mixture was transferred to an ice-bath, diluted with ethyl acetate (50 ml), and then saturated sodium bicarbonate solution (75 ml) was added with vigorous agitation. The organic phase was separated and the aqueous layer extracted again with ethyl acetate (30 ml). The combined organic layers were dried (Na₂ SO₄), filtered and left to stand at room temperature for 41/2 hours over 4 A molecular sieves.

Cyanomethylenetriphenylphosphorane (0.18 g) was dissolved in ethyl acetate (30 ml). The reaction solution was filtered to remove the sieves and then treated with the solution of phosphorane. The reaction solution was reduced in volume (in vacuo) to about 30 ml and left at room temperature for 1 hour. The solution was evaporated to dryness and chromatographed rapidly through a column (5 g) of silica gel (<230 mesh) eluting with 1:1 ethyl acetate: 60°-80° petroleum ether. The product (62 mg) (containing some Ph₃ P═O) was triturated with 1:1 ethyl acetate:petroleum-ether 60°-80° to give the ester (61) (12 mg), as a white solid, ν_(max) (CHCl₃) 2225 (C═N), 1790 (β-lactam and lactone), 1745 (ester), 1640 (side chain double bond), 1615 (ring double bond) cm⁻¹.

The concentrations of this compound required to inhibit the growth of the following bacteria are given below:

    ______________________________________                                         Organism           μg/ml (agar)                                             ______________________________________                                         Citrobacter freundii E8                                                                           7.3                                                         Enterobacter cloacae N1                                                                           22                                                          E. coli 0111       7.3                                                         Klebsiella aerogenes                                                                              7.3                                                         Proteus mirabilis C977                                                                            66.6                                                        Proteus morganii I 580                                                                            22                                                          Proteus rettgeri WM 16                                                                            22                                                          Proteus vulgaris WO 91                                                                            66.6                                                        Salmonella typhimurium                                                                            7                                                           Serratia marcescens US20                                                                          22                                                          Shigella sonnei MB 11967                                                                          22                                                          Staph. aureus Oxford                                                                              2.4                                                         Staph. aureus Russell                                                                             2.4                                                         ______________________________________                                    

EXAMPLE 20 Benzyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR87## (i) Preparation of benzyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR88##

The phosphorane (62) (500 mg) in ethyl acetate (60 ml) was treated with trifluoroacetic acid (0.7 ml). After cooling to -70° ozone was passed into the solution until it became pale blue. Argon was then passed through to remove excess ozone and then triphenylphosphine (250 mg) in ethyl acetate (5 ml) was added. After stirring for 5 minutes the reaction flask was transferred to an ice-bath and saturated aqueous sodium bicarbonate (50 ml) was added. After stirring vigorously for 40 minutes the mixture was dilutd with more ethyl acetate, and the organic phase washed with brine, dried over magnesium sulphate and evaporated to a gum. Chromatography on silica gel, eluting with ethyl acetate-petroleum ether mixtures gave the bicyclo compound (63) as an oil (110 mg). ν_(max) (CHCl₃), 1782, 1725 cm⁻¹. δ ppm (CDCl₃) 2.68 (1H, ddd, J 16 Hz, 9 Hz, 3 Hz, C4-H); 2.90 (1H, ddd, J 16 Hz, 9 Hz, 3 Hz, C4-H), [2.92 (1H, dd, J 16 Hz, 3.5 Hz) and 3.45 (1H, dd, J 16 Hz, 5.5 Hz), collapsing to ABq J 16 Hz on irradiation at δ 4.23, C6-CH₂ ], 4.24 (1H, m. collapsing to d, J 5.5 Hz on irradiation at δ 2.80, C5-H), 5.20 (2H, s, CH₂ Ph), 6.44 (1H, t, J 3 Hz, collapsing to s on irradiation at δ 2.80 (C3-H), 7.30 (5H, s, Ph) (Found: M, 243.0883 C₁₄ H₁₃ NO₃ requires M, 243.0895).

EXAMPLE 21 t-Butyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR89## (i) Preparation of 4-allyl-1-(1-hydroxy-1-tert-butyloxycarbonylmethyl)azetidin-2-one ##STR90##

tert-Butyl glyoxylate hydrate (6.22 g) in benzene (120 ml) was refluxed for 1 hour in a Dean-Stark apparatus to remove the water. The azetidinone (18) (2.31 g) was then added and the reaction mixture refluxed for 4 hours. Chromatography of the crude product as in Example 4(iv) gave the alcohol (64) as a pale yellow oil (4.48 g). ν_(max) (CHCH₃) 3490, 1755, 1735, 1640 (weak)cm⁻¹ δ ppm (CDCl₃) 1.50 (9H, s, But), 2.20-3.25 [4H, 2.66 (1H, dd, J 3 Hz, 14 Hz, C3-H), and 3.09 (1H, dd, J 14 Hz, 5 Hz, C3-H) obscurring 2H, CH₂ ]; 3.68-4.10 (1H, m, C4-H), 4.47 (1H, broad s, exch. D₂ O, OH); 4.98-5.37 (3H, m, sharpening with D₂ O), 5.52-6.23 (1H, m, CH═CH₂). M⁺ at m/e 241 and (m/e +1).

(ii) Preparation of 4-allyl-1-(1-tert-butyloxycarbonyl-1-triphenylphosporanylidene methyl)azetidine-2-one ##STR91##

A stirred solution of the alcohol (64) (4.2 g) in dry tetrahydrofuran (120 ml) under argon, was cooled to -20°, and treated with lutidine (4.03 ml) in tetrahydrofuran (15 ml). Thionyl chloride (2.54 ml) in tetrahydrofuran (15 ml) was added dropwise. After allowing to reach 0° over 30 minutes, the solution was filtered, the lutidine hydrochloride being washed with toluene.

The combined filtrate and washings were evaporated to dryness. The residue was taken up in dry dioxan (100 ml) and treated with lutidine (4.03 ml) and triphenylphosphine (9.1 g). After stirring at room temperature overnight, the phosphorane (65) was isolated as in Example 4(v) and obtained as white crystals (4.62 g) from ether mp. 188°-9°, ν_(max) (CHCl₃) 1730, 1638, 1610 cm⁻¹ (Found: C, 74.1; H, 6.8; N, 3.0. P, 6.2% C₃₀ H₃₂ NO₃ P requires C, 74.2, H, 6.6, N, 2.9, P, 6.4%).

(iii) Preparation of tert-Butyl 7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate ##STR92##

The phosphorane (65) (242 mg) in ethyl acetate (15 ml) was treated with trifluoroacetic acid (0.38 ml). After cooling to -70°, ozone was passed into the solution until it became pale blue. After passing argon through to remove excess ozone, triphenylphosphine (131 mg) in ethyl acetate (1 ml) was added. After stirring for 5 minutes the reaction flask was transferred to an ice-bath and saturated aqueous sodium bicarbonate (20 ml) was added. The mixture was stirred vigorously for 30 minutes and the organic phase separated and washed with water. The aqueous phase was re-extracted with ethyl acetate. The combined organic extracts were dried over magnesium sulphate, evaporated and the residue chromatographed on silica gel eluting with ethyl acetate-petroleum ether mixtures, to give the bicyclic compound (66) as an oil (50 mg) ν_(max) (CHCl₃) 1780, 1710, 1610 cm⁻¹. δ ppm (CDCl₃) 1.49 (9H, s, Bu^(t)), 2.70 (1H, ddd, J 19 Hz, 10 Hz, 2 Hz, C4-H), 2.87 (1H, ddd, J 19 Hz, 9 Hz, 2 Hz, C4-H), 2.86 (1H, dd, J 14 Hz, 2.5 Hz, C6-H), 3.40 (1H, dd, J 14 Hz, 5 Hz, C6-H), 3.99-4.33 (1H, m, C5-H), 4.26 (1H, t, J 2 Hz, C3-H). (Found: M, 209.1050 C₁₁ H₁₅ NO₃ requires M, 209.1052).

EXAMPLE 22 t-Butyl 3-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate ##STR93## (i) Preparation of 4-(propan-2-one)azetidin-2-one ##STR94##

4-Allyl-azetidin-2-one (18) (0.22 g, 2 mmoles) and mercuric acetate (0.64 g, 2 mmoles) were stirred at room temperature for 2 hours in methanol (6 ml). This solution was added to a mixture of cupric chloride dihydrate (1.03 g, 6 mmoles) and palladous chloride (0.034 g, 0.2 mmoles) in methanol (6 ml). After heating for 1 hour at 60° C., the reaction mixture was cooled and saturated aqueous sodium hydrogen carbonate was added until the solution was at pH 9. The reaction mixture was filtered and the methanol removed under reduced pressure. Extraction of the aqueous phase with ethyl acetate (3×25 ml) followed by drying (MgSO₄) and removal of solvent, gave a green oil. Chromatography (silica eluted with pet. ether-ethyl acetate-ethanol) gave the ketone (67) (0.17 g, 70%) as an oil, ν_(max) (CHCl₃) 3420, 3000, 1760, and 1720 cm⁻¹ ; δ (CDCl₃) 2.14 (3H, s, CH₃), 2.4-3.4 (4H, m, methylenes), 3.86 (1H, m, C4-H), and 6.75 (1H, br, NH), (Found: M, 127.0628. C₆ H₉ NO₂ requires M, 127.0634).

(ii) Preparation of 1-(1-Hydroxy-1-t-butoxycarbonylmethyl)-4-(propan-2-one)azetidin-2-one ##STR95##

t-Butyl glyoxylate hydrate (0.3 g, 2.33 mmoles) was heated under reflux in benzene (10 ml) for 1 hour in an apparatus with provision for water removal. The ketone (67) (0.14 g, 1.1 mmoles) in dry benzene (3 ml) was added and the mixture was heated under reflux for 4 hours. Removal of solvent under reduced pressure followed by chromatography (silica eluted with pet. ether-ethyl acetate) gave the keto-alcohol (68) (0.196 g, 82%),δ (CDCl₃) 1.55 (9H, s, t-Bu), 2.23 (3H, s, CH₃), 2.5-3.5 (4H, m, methylenes), 4.20 (1H, m, C4-H), and 4.6-5.5 (2H, m, CHOH); and unchanged ketone (0.022 g).

(iii) Preparation of 1-(1-t-butoxycarbonyl-1-triphenylphosphoranylidenemethyl)-4-(propan-2-one)azetidin-2-one ##STR96##

To a stirred solution of the keto-alcohol (68) (0.196 g, 0.763 mmoles) in dry tetrahydrofuran (5 ml) at -20° C. was added in turn 2,6-lutidine (0.163 g, 0.177 ml, 1.52 mmoles) and thionylchloride (0.181 g, 0.11 ml, 1.52 mmoles) in tetrahydrofuran (1 ml). The stirring was continued at -20° C. for 20 minutes. The solution was filtered, and the solvent was removed under reduced pressure and the residue was dried by azeotroping twice with toluene (10 ml). The resulting slurry was dissolved in dioxan (7 ml) and 2,6-lutidine (0.163 g, 0.177 ml, 1.52 mmoles) and triphenylphosphine (0.4 g, 1.52 mmoles) were added in turn. After stirring for 16 hours, the solution was filtered and the solvent was removed under reduced pressure. Chromatography (silica eluted with pet. ether-ethyl acetate) gave a semi-crystalline oil which could be crystallized by the addition of ether to give the phosphorane (69) (0.255 g, 70%) as white needles m.p. 176.5°-177.5°, ν_(max) (CHCl₃) 2990, 1740, 1720, and 1640 cm⁻¹, δ (CDCl₃) 0.9 (9H, s, t-Bu), 1.4 (3H, s, CH₃), 2.18 (4H, m, methylenes), 3.14 (1H, m, C4-H), and 7.1-7.9 (15H, m, Ph). (Found: C, 71.8; H, 6.4; N, 2.7%. C₃₀ H₃₂ NO₄ P requires C, 71.8; H, 6.4; N, 2.8%)

(iv) Preparation of t-Butyl 3-methyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR97##

The phosphorane (69) (0.062 g, 0.124 mmoles) was heated in dry toluene (5 ml) under argon for 11/2 hours at 100° C. The toluene was removed under reduced pressure and the residue chromatographed (silica eluted with pet. ether-ethyl acetate) to give the bicyclic product (70) (0.023 g, 83%) as an oil having ν_(max) (CHCl₃) 2970, 1775, 1700, and 1635 cm⁻¹, λ_(max) (EtOH) 272 nm (ε 4000). δ (CDCl₃) 1.51 (9H, s, tBu), 2.04 (3H, t, J 1.5 Hz, CH₃), 2.73 (2H, br d, J 9 Hz, C4-H), 2.77 (1H, dd, J 3, 16 Hz, C6-H), 3.35 (1H, dd, J 6, 16 Hz, C6-H), and 4.05 (1H, m, C5-H). (Found: M, 223.1212. C₁₂ H₁₇ NO₃ requires M, 223.1208).

EXAMPLE 23 p-Nitrobenzyl 3-methyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR98## (i) Preparation of 1-(1-Hydroxy-1-p-nitrobenzyloxycarbonylmethyl)-4-(propan-2-one)azetidin-2-one ##STR99##

p-Nitrobenzyl glyoxylate hydrate (2.64 g, 11.6 mmoles) was heated under reflux in benzene (50 ml) for 1 hour in an apparatus with provision for water removal. The ketone (67) (0.8 g, 5.5 mmoles) in dry benzene (10 ml) was added and the mixture was heated under reflux for 7 hours. Removal of solvent under reduced pressure followed by chromatography (silica eluted with pet. ether-ethyl acetate) gave the keto-alcohol (71) (1.39 g, 75%) as a colourless oil, ν_(max) (CHCl₃) 3450, 1760, 1715, 1605, 1520 and 1345 cm⁻¹, δ (CDCl₃) 2.17 (3H, d, CH₃), 2.46-3.54 (4H, m, β-lactam and α-ketomethylenes), 4.20 (1H, m, C4-H), 4.50-5.8 (2H, m, CHOH), 5.40 (2H, d, benzylmethylene) and 7.50-8.40 (4H, m, aromatic).

(ii) Preparation of 1-(1-p-Nitrobenzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)-4-(propan-2-one)azetidin-2-one ##STR100##

To a stirred solution of the keto-alcohol (71) (0.611 g, 1.84 mmoles) in dry tetrahydrofuran (13 ml) at -20° C. was added in turn 2,6-lutidine (0.39 g, 0.424 ml, 3.68 mmoles) and thionyl chloride (0.433 g, 0.264 ml, 3.68 mmoles) in tetrahydrofuran (2 ml). The stirring was continued at -20° C. for 20 minutes. The solution was filtered, and the solvent was removed under reduced pressure and the residue was dried by azeotroping twice with toluene (20 ml). The resulting slurry was dissolved in dioxan (15 ml) and 2,6-lutidine (0.39 g, 0.424 ml, 3.68 mmoles) and triphenylphosphine (0.95 g, 3.68 mmoles) were added in turn. After stirring for 2 hours, the solution was filtered and the solvent was removed under reduced pressure. Chromatography (silica eluted with pet. ether-ethyl acetate-dioxan) gave the phosphorane (72) (0.73 g, 70%) as a yellow crystals m.p. 185°-187°, ν_(max) (CHCl₃) 2990, 1740, 1715, 1630, 1610, 1520, and 1350 cm⁻¹.

(iii) Preparation of p-Nitrobenzyl 3-methyl-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR101##

The phosphorane (72) (0.2 g, 0.345 mmoles) was heated in dry toluene (10 ml) under argon for 10 hours at 100° C. The toluene was removed under reduced pressure and the residue chromatographed (silica eluted with pet. ether-ethyl acetate) to give the bicyclic product (73) (0.05 g, 64%) as colourless needles m.p. 116° (from ethyl acetate pet.ether) having ν_(max) (CHCl₃) 3000, 1785, 1725, 1635, 1610, 1415, and 1350 cm⁻¹, δ (CDCl₃) 2.12 (3H, s, CH₃), 2.7-3.0 (3H, m, C4-H and C-6H), 3.4 (1H, dd, J 6, 16 Hz, C6-H), 4.12 (1H, m, C5-H), 5.3 (2H, ABq, J 14 Hz, benzylic) and 7.45-8.25 (4H, m, aromatic) and unchanged phosphorane (0.05 g).

EXAMPLE 24 Methyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR102## (i) Preparation of 4-allyl-1-(1-hydroxy-1-methoxycarbonylmethyl)azetidin-2-one ##STR103##

Methyl glyoxylate hydrate (9.75 g) in benzene (500 ml) was refluxed for 1 hour in a Dean-Stark apparatus to remove the water. The azetidinone (18) (2.68 g) was then added and the reaction mixture refluxed for 2 hours. A further portion of the azetidinone (1.34 g) (18) was then introduced, and refluxing continued for 3 hours. Chromatography of the crude product as in Example 4 (iv) gave the alcohol (74) as a pale yellow oil (5.33 g). ν_(max) (CHCl₃) 3500, 3350 (broad), 1760-1740 (strong), 1640 (weak) cm⁻¹. δ ppm (CDCl₃) 2.24-2.90 (3H, m, including [1H, dd, J 3 Hz. 14.5 Hz at δ 2.68]), 3.11 (1H, dd, J 4.5 Hz, 14.5 Hz), 3.72-4.42 (5H, including [3H, s, at δ 3.90], 1 H, exch. D₂ O), 5.00-6.29 (4H, m including [1H, s, at δ 5.48]).

(ii) Preparation of 4-allyl-1-(1-methoxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidin-2-one ##STR104##

A stirred solution of the alcohol (74) (5.23 g) in dry tetrahydrofuran (150 ml) under argon, was cooled to -20°, and treated with lutidine (6.06 ml) in tetrahydrofuran (20 ml). Thionyl chloride (3.83 ml) in tetrahydrofuran (20 ml) was added dropwise. After allowing to reach 0° over 20 minutes, the solution was filtered, the lutidine hydrochloride being washed with toluene.

The combined filtrate and washings were evaporated to dryness. The residue was taken up in dry dioxan (150 ml) and treated with lutidine (6.06 ml) and triphenylphosphine (13.7 g). After stirring at room temperature, overnight, the phosphorane (75) was isolated as in Example 4 (v) and obtained as white crystals (7.3 g) from ether m.p. 208°-212°. ν_(max) (CHCl₃) 1738, 1640, 1620 cm⁻¹ (Found: C, 72.6; H, 5.9; N, 3.0%. C₂₇ H₂₆ NO₃ P requires C, 73.1; H, 5.9; N, 3.2%.

(iii) Preparation of methyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR105##

The phosphorane (75) (0.886 g) in ethyl acetate (60 ml) was treated with trifluoroacetic acid (1.52 ml). After cooling to -70°, ozone was passed into the solution until it became pale blue. After passing argon through to remove excess ozone, triphenylphosphine (534 mg) in ethyl acetate (5 ml) was added. After stirring for 10 minutes the reaction flask was transferred to an ice-bath and saturated aqueous sodium bicarbonate (50 ml) was added. The mixture was stirred vigorously for 1 hour, and then extracted and chromatographed as in Example (21,iii) to give the bicyclic compound (76) (150 mg). Crystallisation from ethyl acetate/petroleum ether (60°-80°) gave (76) as pale yellow needles, m.p. 72°-72.5°. ν_(max) (CHCl₃) 1785, 1738. λ_(max) (EtOH) 272 nm (ε 4,500). δ ppm (CDCl₃) 2.66 (1H, ddd, J 3 Hz, 8.5 Hz, 19 Hz), 3.04 (1H, ddd, J 3 Hz, 11.5 Hz, 19 Hz), 2.90 (1H, dd, J 3 Hz, 16.5 Hz), 3.45 (1H, dd, J 5.5 Hz, 16.5 Hz), 3.79 (3H, s), 4.23 (1H, m), 6.43 (1H, t, J 3 Hz) (Found: C, 57.47; H, 5.63; N, 8.24% C₈ H₉ NO₃ requires C, 57.49; H, 5.39; N, 8.38%) (Found: M, 167.0589 C₈ H₉ NO₃ requires M, 167.0582).

EXAMPLE 25 p-Nitrobenzyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR106## (i) Preparation of 4-allyl-1-(1-hydroxy-1-p-nitrobenzyloxycarbonylmethyl)azetidin-2-one ##STR107##

p-Nitrobenzyl glyoxylate hydrate (6.8 g) in benzene (120 ml) was refluxed for one hour with removal of water (Dean-Stark). The azetidinone (18) (3 g) was added and the mixture refluxed for two hours. The solution was cooled, the solvent evaporated and the residue chromatographed. Elution with 80% ethyl acetate/petroleum ether (60°-80°) gave the product (77). The product was re-chromatographed to complete purification and collected as an oil (3.2 g) (37%) ν_(max) (CHCl₃) 3500 (OH), 1755 (br), 1530, 1355 cm⁻¹. δ ppm (CDCl₃) 2.39 (2H, m, CH₂ CH═CH₂), 2.61 (1H, dd, J 16 Hz, 4 Hz, C3-H), 3.05 (1H, dd, J 16 Hz, 6 Hz, C3-H), 3.92 (1H, m, C4-H), 4.63 (1H, m, collapsing to a singlet on D₂ O exchange, CH-OH); 4.80 to 5.80 (6H, complex pattern including CH₂ Ph-p-NO₂ at 5.35, OH [exchangeable] and CH═CH₂), 7.56 and 8.23 (4H, ABq, J 8 Hz, aromatics.)

(ii) Preparation of 4-allyl-1-(1-p-nitrobenzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one ##STR108##

A stirred solution of the alcohol (77) (1.6 g) in dry THF (100 ml) was treated with 2,6 lutidine (1.07 g) and thionyl chloride (1.19 g) in THF (20 ml) at -20° and stirring continued for 20 minutes. The mixture was filtered, the solvent evaporated and the residue azeotroped twice with toluene. It was dissolved in dioxan (100 ml) and 2,6-lutidine (1.01 g) and triphenylphosphine (2.62 g) were added. The reaction was stirred at room temperature overnight and filtered. The solvent was evaporated and the residue chromatographed to yield the product, (78) after de-colourising with charcoal (ethanol/ethyl acetate solution) and trituration of the evaporated solution with ether, as a light yellow solid (1.5 g; 53%) m.p. 182°-3° ν_(max) (CHCl₃) 1740, 1620, 1525, 1355 cm⁻¹. (Found: C, 70.26; H, 5.33; N, 4.80. C₃₃ H₂₉ N₂ O₅ P requires C, 70.21; H, 5.14; N, 4.96%).

(iii) Preparation of p-nitrobenzyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR109##

The phosphorane (78) (1.0 g) in ethyl acetate (50 ml) was treated with trifluoroacetic acid (1.5 ml) (R.T.) and then cooled to -70°. Ozone was passed through the solution until it became slightly blue. Excess ozone was then removed by bubbling through argon, and then triphenylphosphine (0.51 g) in ethyl acetate (10 ml) was added. The reaction flask was transferred to an ice-bath and the reaction solution stirred vigorously and treated with aqueous sodium bicarbonate solution until slightly basic (pH8). The organic phase was separated, dried (MgSO₄), filtered and left to stand at room temperature for 2.5 h. The solution was evaporated to a gum and chromatographed on silica gel (Merck 60 <230 mesh) eluting with 1:1 ethyl acetate-petroleum ether (60°-80°). The product (79) was obtained as a yellow crystalline solid (0.21 g; 41%), m.p. 144°-147°; λ_(max) (EtOH) 270 nm (ε, 13,550), ν_(max) (CHCl₃ ) 1780, 1730, 1610, 1525, 1350 cm⁻¹. δ ppm (CDCl₃) 2.55-3.15 (2H, m, C4-H₂), 2.95 (1H, dd, J 16 Hz, 3 Hz, C6-H), 3.50 (1H, dd, J 16 Hz, 6 Hz, C6-H), 4.10-4.40 (1H, m, C5-H), 5.21 and 5.41 (2H, ABq, J 12 Hz, CH₂ PhpNO₂), 6.53 (1H, t, J 2.5 Hz), 7.55 (2H, d, J 8 Hz), 8.15 (2H, d, J 8 Hz) (Found: C, 58.2; H, 4.2; N, 9.5%; M, 288.0773 C₁₄ H₁₂ N₂ O₅ requires C, 58.3; H, 4.2; N, 9.7%; M, 288.0746).

EXAMPLE 26 Phthalidyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR110## (i) Preparation of 4-allyl-1-(1-phthalidyloxycarbonyl-1-tris-p-methoxyphenylphosphoranylidenemethyl)azetidin-2-one ##STR111##

Allylazetidinone (18) (6.3 g), glyoxylic acid monohydrate (5.52 g), 30 4 A° molecular sieves (1/8" pellets) and dry DMF (30 ml) were stirred for 6 hours at room temperature. The mixture was cooled to 0° C. and powdered potassium carbonate (4.14 g) was added. The mixture was allowed to warm up to room temperature and stirred for 5 minutes. Bromophthalide (12.8 g) was added and the mixture was stirred for 16 hours. The resulting solution was poured onto N/10 hydrochloric acid (250 ml) and ethyl acetate (250 ml). The organic layer was washed once more with N/10 hydrochloric acid (250 ml) and then with saturated aqueous sodium hydrogen carbonate (250 ml) and brine (250 ml); each aqueous washing being extracted once with ethyl acetate (250 ml). The combined organic extracts were dried (Na₂ SO₄) and the solvent removed under reduced pressure to give an oil (10 g).

A stirred solution of this oil in dry tetrahydrofuran (250 ml), under argon, was cooled to -20°, and treated with 2,6-lutidine (7.6 ml) followed by thionyl chloride (4.8 ml in 30 ml tetrahydrofuran). After stirring for 20 minutes at -20° the mixture was brought to room temperature and filtered. The precipitated solid was washed with toluene and the combined filtrate and washings were evaporated to dryness under reduced pressure. The residue was dissolved in toluene and re-evaporated to dryness to remove excess thionyl chloride.

The oil obtained was dissolved in dry tetrahydrofuran (250 ml) and treated with 2,6-lutidine (7.6 ml) and tris-p-methoxyphenylphosphine (15 g). After stirring for 16 hours, the mixture was filtered and the solvent removed from the filtrate under reduced pressure. The filtrant was dissolved up in ethyl acetate (250 ml) and N/10 hydrochloric acid (250 ml) and added to the evaporated filtrate. The organic layer was separated and washed with N/10 hydrochloric acid (250 ml) and brine; each aqueous washing being extracted with ethyl acetate (250 ml). The combined organic extracts were dried (Na₂ SO₄) and the solvent removed under reduced pressure. Chromatography on silica gel eluting with petroleum ether-ethyl acetate-dioxan mixtures gave the required phosphorone (80), initially as a foam (10 g), which crystallised on addition of ether; (6.25 g); m.p. 136°-9° (ethyl acetate-petroleum ether); ν_(max) (CHCl₃) 3000, 1780, 1745, 1650, 1605, 1260, and 1115 cm⁻¹ ; (Found: C, 64.98; H, 5.24; N, 2.13. C₃₇ H₃₄ PNO₈.2H₂ O requires C, 64.68; H, 5.58; N, 2.04%).

(ii) Preparation of phthalidyl 7-oxo-1-azabicyclo[3,2,0]-hept-2-ene-2-carboxylate ##STR112##

The phosphorane (80) (0.325 g) was dissolved in 5:1 ethyl acetate/trifluoroacetic acid (12 ml). The solution was left at room temperature for 10 minutes and then cooled to -70°. Ozone was then passed through the solution until it became pale blue. Argon was passed through the solution to remove excess ozone and then tris-p-methoxyphenylphosphine (0.17 g) in ethyl acetate (2 ml) was added. The mixture was warmed up to 0° C. with an ice bath and then saturated potassium hydrogen carbonate solution (10 ml) was added carefully with vigorous agitation. The layers were separated and the aqueous layer was extracted twice more with ethyl acetate (2×10 ml). The combined organic layers were pre-dried (Na₂ SO₄) and then left standing over 4 A° molecular sieves and di-isopropylaminomethylpolystyrene (0.4 g) for 16 hours. The solution was filtered and the solvent removed under reduced pressure to give a yellow oil. Rapid chromatography on florisil eluting with 1:1 petroleum ether-ethyl acetate give the phthalidyl ester (81) as a white solid (17 mgms) having ν_(max) (CHCl₃) 1800, 1755, 1615 m and 985 cm⁻¹, δ (CDCl₃) 2.7-3.2 (3H, m, C4-H₂ and C6-H_(A)), 3.50 (1H, 2×dd, J 6, 17 Hz, C6-H_(B)), 4.23 (1H, m, C5-H), 6.49 and 6.62 (1H, 2×t, J 3 Hz, C3-H), 7.45 and 7.51 (1H, 2×s, phthalidyl methine), and 7.55-7.95 (4H, m, aromatic).

The concentrations of this compound required to inhibit the growth of the following bacteria are given below:

    ______________________________________                                         Organism            μg/ml (agar)                                            ______________________________________                                         B. subtilis A       20                                                         Citrobacter freundii E8                                                                            20                                                         Enterobacter cloacae N1                                                                            20                                                         E. coli 0111        20                                                         Klebsiella aerogenes A                                                                             20                                                         Proteus mirabilis C977                                                                             20                                                         Pseudomonas aeruginosa A                                                                           160                                                        Salmonella typhimurium CT10                                                                        20                                                         Serratia marcescens VS20                                                                           20                                                         Staph. aureus Oxford                                                                               20                                                         Staph. aureus Russell                                                                              20                                                         ______________________________________                                    

EXAMPLE 27 Pivaloyloxymethyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate ##STR113## (i) 4-Allyl-1-(1-pivaloyloxymethoxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one ##STR114##

4-Allylazetidin-2-one (18) (2.0 g) and glyoxylic acid monohydrate (1.75 g) were stirred together in dry dimethylformamide (10 ml) for 6 hours in the presence of 4 A molecular sieves. The mixture was then cooled in an ice bath and powdered potassium carbonate (1.31 g) was added. It was allowed to warm to room temperature and stirred for 5 minutes prior to adding pivaloyloxymethyl bromide (5.3 g). The reaction was stirred overnight and then poured into a mixture of N/10 hydrochloric acid (80 ml) and ethyl acetate (80 ml). The organic phase was separated and the aqueous solution washed with further ethyl acetate (50 ml). The ethyl acetate solutions were combined, washed with saturated aqueous sodium bicarbonate, then brine and dried over sodium sulphate. It was concentrated in vacuo to give the crude ester (82) as a yellow oil (4.7 g).

The crude ester (82) (4.7 g) was dissolved in dry tetrahydrofuran (80 ml) and stirred at -20° under argon. It was treated with 2,6-lutidine (3.7 ml) followed over a period of 5 minutes by a solution of thionyl chloride (2.3 ml) in tetrahydrofuran (20 ml). The reaction was allowed to warm to ambient temperature over a period of 1/2 hour and then filtered. The solid was washed with dry toluene and the combined filtrates was concentrated under reduced pressure. The vestigial thionyl chloride was removed by two further evaporations from toluene to give the chloride (83) as a brown oil.

The chloride (83) was dissolved in dry dioxane (80 ml) and treated with triphenylphosphine (8.2 g) and 2,6-lutidine (3.7 ml). The reaction mixture was stirred overnight and then filtered; the filtrate concentrated and redissolved in ethyl acetate (100 ml). This solution was washed free of base with N/10 hydrochloric acid (ca 100 ml) and then washed with brine and dried over sodium sulphate. The solution was concentrated and then chromatographed on silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 7:3 to give a foam. This was dissolved in diethyl ether (20 ml) and a white solid rapidly crystallized out. This was 4-allyl-1-(1-pivaloyloxymethoxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (84) which was obtained in a yield of 3.06 g; m.p. 140°-142° (ethyl acetate/60°-80° petroleum ether); ν_(max) (CHCl₃) 2980, 1740 and 1635 cm⁻¹.

(ii) Pivaloyloxymethyl 70 oxo-1-azabicyclo[3,2,0) hept-2-ene-2-carboxylate ##STR115##

A solution of 4-allyl-1-(1-pivaloyloxymethoxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidine-2-one (84) (0.50 g) in ethyl acetate (15 ml) was stirred in a bath at 10° and treated with trifluoroacetic acid (3 ml). After 15 minutes the solution was cooled to -78° and ozone was passed through the solution until reaction was complete. Excess ozone was blown off in a stream of argon and an ethyl acetate solution of triphenylphosphine (0.24 g) was added. After a period of 30 minutes the reaction flask was transferred to an ice bath and ethyl acetate (40 ml) followed by saturated aqueous sodium bicarbonate (90 ml) were added with vigorous stirring. The ethyl acetate phase was then immediately separated, washed with brine and dried by stirring over calcium chloride for 15 minutes. The solution was then filtered and 4 A molecular sieves added to the solution. The supernatent solution was concentrated 3 hours later and quickly chromatographed on a small column of silica gel 60 (<230 mesh) eluting with ethyl acetate/60°-80° petroleum ether 1:1. Further purification was effected on a small column of Florisil (200-300 mesh) eluting with ethyl acetate/60°-80° petroleum ether 3:7. This gave pivaloyloxymethyl 7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate (85) (0.022 g) as a colourless gum; ν_(max) (CHCl₃) 2970, 1790, 1750 and 1610 cm⁻¹ ; τ (CDCl₃) 3.51 (1H, t, J 3Hz, C3-H), 4.15 and 4.24 (2H, ABQ, J 51/2 Hz, OCH₂ O), 5.78 (1H, tdd, J 9, 51/2 and 3 Hz, C5-H), 6.54 (1H, dd, J 17 and 51/2 Hz, C6-H), 7.03 (1H, ddd, J 19, 9 and 3 Hz, C4-H), 7.10 (1H, dd, J 17 and 3 Hz, C6-H), 7.31 (1H, ddd, J 19, 9 and 3 Hz, C4-H) and 8.80 (9H, s, t-butyl). (M⁺ at m/e 267.1118. C₁₃ H₁₇ NO₅ requires 267.1107). 

What we claim is:
 1. A compound of the formula (II): ##STR116## wherein R₁ is a group such that CO₂ R₁ is a pharmaceutically acceptable ester group; A₁ is hydrogen; and A₂ is a group CR₂ R₃ R₄ wherein R₂ is hydrogen or hydroxyl; R₃ is hydrogen or lower alkyl; and R₄ is CHX wherein X is oxygen or CR₆ R₇ wherein R₆ is hydrogen, lower alkyl, phenyl, CN, COR₈ or CO₂ R₈ wherein R₈ is lower alkyl, phenyl or benzyl and R₇ is hydrogen or lower alkyl or R₇ is joined to R₆ to form part of a carbocyclic ring of 5 to 7 carbon atoms or R₄ is CH═CHCO₂ R₉, CH═CHCOR₉ or CH═CHR₁₀ wherein R₉ is methyl, ethyl or benzyl and R₁₀ is hydrogen, methyl, ethyl or benzyl.
 2. A compound according to claim 1 wherein R₄ is CHO, CH═CHCO₂ R₉, CH═CHCOR₉ or CH═CHR₁₀ wherein R₉ is methyl, ethyl or benzyl and R₁₀ is hydrogen, methyl, ethyl or benzyl.
 3. A compound according to claim 1 wherein R₃ is hydrogen or methyl.
 4. A compound according to claim 1 which has the cis-configuration about the β-lactam ring.
 5. A compound according to claim 1 which has the trans-configuration about the β-lactam ring.
 6. A compound according to claim 1 wherein R₁ is alkyl of up to 12 carbon atoms, alkenyl groups of up to 8 carbon atoms, phenyl or benzyl or said alkyl, alkenyl, phenyl or benzyl substituted by lower alkoxyl, lower acyloxyl, halogen or nitro.
 7. A compound according to claim 1 wherein R₁ is lower alkyl unsubstituted or substituted by lower alkoxyl.
 8. A compound according to claim 1 wherein R₁ is benzyl unsubstituted or substituted by lower alkoxyl, nitro or chlorine.
 9. A compound according to claim 1 wherein R₁ is a group of the sub-formula (a) or (b): ##STR117## wherein A₃ is hydrogen or methyl; A₄ is lower alkyl, lower alkoxyl, phenyl, phenoxyl, benzyl or benzyloxyl; A₅ is hydrogen, methyl or methoxyl; and A₆ is hydrogen, methyl or methoxyl, or R₁ is phthalidyl or phthalimidomethyl.
 10. A compound according to claim 1 wherein R₁ is benzyl.
 11. A compound according to claim 1 wherein R₁ is p-nitrobenzyl.
 12. A compound according to claim 1 wherein R₁ is phthalidyl.
 13. A compound according to claim 1 which is benzyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 14. A compound according to claim 1 which is benzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 15. The compound which is 2,2,2-trichloroethyl-6-(3-methoxycarbonyl2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 16. A compound according to claim 1 which is phthalidyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 17. A compound according to claim 1 which is phthalimidomethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 18. A compound according to claim 1 which is phthalidyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 19. A compound according to claim 1 which is phthalidyl 6-(4-oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 20. A compound according to claim 1 which is pivaloyloxymethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 21. A compound according to claim 1 which is p-nitrobenzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 22. A compound according to claim 1 which is benzyl 6-(3-cyano-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 23. A compound according to claim 1 which is benzyl 6-(4-oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 24. A compound according to claim 1 which is p-bromophenacyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 25. A compound according to claim 1 which is phthalidyl 6-(3-cyano-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 26. A compound of the formula (V): ##STR118## wherein R₁ is a group such that CO₂ R₁ is a pharmaceutically acceptable ester group; and X is an oxygen atom or CR₆ R₇ wherein R₆ is hydrogen, lower alkyl, phenyl, CN, COR₈ or CO₂ R₈ wherein R₈ is lower alkyl, phenyl or benzyl and R₇ is hydrogen or lower alkyl, or R₇ is joined to R₆ to form part of a carbocyclic ring of 5 to 7 carbon atoms.
 27. A compound according to claim 26 wherein X is oxygen.
 28. A compound according to claim 26 wherein X is a CR₆ R₇ group wherein R₆ is hydrogen, lower alkyl, phenyl, CN, COR₈ or CO₂ R₈ wherein R₈ is lower alkyl, phenyl or benzyl and R₇ is hydrogen or lower alkyl or is joined to R₆ to form part of a 5 to 7 carbon atom carbocyclic ring.
 29. A compound according to claim 28 wherein CR₆ R₇ is CHCOR₉ or CHCO₂ R₉ wherein R₉ is methyl, ethyl or benzyl.
 30. A compound according to claim 28 wherein CR₆ R₇ is CHCN.
 31. A pharmaceutical composition useful for treating bacterial infections in humans and animals which comprises an antibacterially effective amount of a compound of the formula (II): ##STR119## wherein R₁ is a group such that CO₂ R₁ is a pharmaceutically acceptable ester group; A₁ is hydrogen; and A₂ is a group CR₂ R₃ R₄ wherein R₂ is hydrogen or hydroxyl; R₃ is hydrogen or lower alkyl; and R₄ is CHX wherein X is oxygen or CR₆ R₇ wherein R₆ is hydrogen, lower alkyl, phenyl, CN, COR₈ or CO₂ R₈ wherein R₈ is lower alkyl, phenyl or benzyl and R₇ is hydrogen or lowr alkyl or R₇ is joined to R₆ to form part of a carbocyclic ring of 5 to 7 carbon atoms or R₄ is CH═CHCO₂ R₉, CH═CHCOR₉ or CH═CHR₁₀ wherein R₉ is methyl, ethyl or benzyl and R₁₀ is hydrogen, methyl, ethyl or benzyl, in combination with a pharmaceutically acceptable carrier.
 32. A composition according to claim 31 wherein R₄ is CHO, CH═CHCO₂ R₉, CH═CHCOR₉ or CH═CHR₁₀ wherein R₉ is methyl, ethyl or benzyl and R₁₀ is hydrogen, methyl, ethyl or benzyl.
 33. A composition according to claim 31 wherein R₃ is hydrogen or methyl.
 34. A composition according to claim 31 wherein the compound has the cis-configuration about the β-lactam ring.
 35. A composition according to claim 31 wherein the compound has the trans-configuration about the β-lactam ring.
 36. A composition according to claim 31 wherein R₁ is alkyl of up to 12 carbon atoms, alkenyl groups of up to 8 carbon atoms, phenyl or benzyl or said alkyl, alkenyl, phenyl or benzyl substituted by lower alkoxyl, lower acyloxyl, halogen or nitro.
 37. A composition according to claim 31 wherein R₁ is lower alkyl unsubstituted or substituted by lower alkoxyl.
 38. A composition according to claim 31 wherein R₁ is benzyl unsubstituted or substituted by lower alkoxyl, nitro or chlorine.
 39. A composition according to claim 31 wherein R₁ is a group of the sub-formula (a) or (b): ##STR120## wherein A₃ is hydrogen or methyl; A₄ is lower alkyl, lower alkoxyl, phenyl, phenoxyl, benzyl or benzyloxyl; A₅ is hydrogen, methyl or methoxyl; and A₆ is hydrogen, methyl or methoxyl or R₁ is phthalidyl or phthalimidomethyl.
 40. A composition according to claim 31 wherein R₁ is benzyl.
 41. A composition according to claim 31 wherein R₁ is p-nitrobenzyl.
 42. A composition according to claim 31 wherein R₁ is phthalidyl.
 43. A pharmaceutical composition useful for treating bacterial infections in humans and animals which comprises an antibacterially effective amount of a compound of the formula (V): ##STR121## wherein R₁ is a group such that CO₂ R₁ is a pharmaceutically acceptable ester group; and X is an oxygen atom or CR₆ R₇ wherein R₆ is hydrogen, lower alkyl, phenyl, CN, COR₈ or CO₂ R₈ wherein R₈ is lower alkyl, phenyl or benzyl and R₇ is hydrogen or lower alkyl, or R₇ is joined to R₆ to form part of a carbocyclic ring of 5 to 7 carbon atoms, in combination with a pharmaceutically acceptable carrier.
 44. A composition according to claim 43 wherein X is oxygen.
 45. A composition according to claim 43 wherein X is a CR₆ R₇ group wherein R₆ is hydrogen, lower alkyl, phenyl, CN, COR₈ or CO₂ R₈ wherein R₈ is lower alkyl, phenyl or benzyl and R₇ is hydrogen or lower alkyl or R₇ is joined to R₆ to form part of a carbocyclic ring of 5 to 7 carbon atoms.
 46. A composition according to claim 45 wherein CR₆ R₇ is CHCOR₉ or CHCO₂ R₉ wherein R₉ is methyl, ethyl or benzyl.
 47. A composition according to claim 45 wherein CR₆ R₇ is CHCN.
 48. A composition according to claim 31 wherein the compound is benzyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 49. A composition according to claim 31 wherein the compound is benzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 50. A pharmaceutical composition useful for treating bacterial infections in humans and animals which comprises an antibacterially effective amount of 2,2,2-tricholoroethyl-6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclohept-2-ene-2-carboxylate, in combination with a pharmaceutically acceptable carrier.
 51. A composition according to claim 31 wherein the compound is phthalidyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 52. A composition according to claim 31 wherein the compound is phthalimidomethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 53. A composition according to claim 31 wherein the compound is phthalidyl 6-(2-oxoethyl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 54. A composition according to claim 31 wherein the compound is phthalidyl 6-(4-oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 55. A composition according to claim 31 wherein the compound is pivaloyloxymethyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 56. A composition according to claim 31 wherein the compound is p-nitrobenzyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 57. A composition according to claim 31 wherein the compound is benzyl 6-(3-cyano-2-propen-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 58. A composition according to claim 31 wherein the compound is benzyl 6-(4-oxo-2-penten-1-yl)-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 59. A pharmaceutical composition useful for treating bacterial infections in humans and animals which comprises an antibacterially effective amount of p-bromophenacyl 6-(3-methoxycarbonyl-2-propen-1-yl)-7-oxo-1-azabicyclohept-2-ene-2-carboxylate, in combination with a pharmaceutically acceptable carrier.
 60. A composition according to claim 31 wherein the compound is phthalidyl 6-(3-cyano-2-propen-1-yl(-7-oxo-1-azabicyclo[3,2,0]hept-2-ene-2-carboxylate.
 61. A composition according to claim 31 in unit dosage form wherein each dosage unit contains 50-500 mg of said compound.
 62. A composition according to claim 31 in parenteral administration form. 